针对从弹射程序启动到飞行员着陆之间的各个阶段,建立了能够对横滚、俯冲等复杂弹射条件进行计算的数学模型.结合某型座椅的具体参数与气动力数据,针对具体算例求解了弹射救生过程,与实验结果进行了对比.根据模型的计算结果,以动态响应指数(DRI)对不同弹射初速下的损伤风险做出评估,并指出了在不同速度下气动过载的影响.

针对从弹射程序启动到飞行员着陆之间的各个阶段,建立了能够对横滚、俯冲等复杂弹射条件进行计算的数学模型.结合某型座椅的具体参数与气动力数据,针对具体算例求解了弹射救生过程,与实验结果进行了对比.根据模型的计算结果,以动态响应指数(DRI)对不同弹射初速下的损伤风险做出评估,并指出了在不同速度下气动过载的影响.

目的 通过模拟高空跳伞着陆训练环境测定不同高度半蹲式跳伞着陆状态下的踝关节角速度、地面垂直反作用力，为预防跳伞着陆踝部损伤提供生物力学依据。方法 募集18名健康志愿者，包括空军地勤人员9名、职业跳伞人员9名。两组受试者身高、体重的差异无统计学意义。受试者分别从30 cm和60 cm高的跳台以半蹲式跳伞着陆并腿姿势跳落到测力台上。高速摄像机记录着陆过程，测定踝关节跖屈角位移及时间、地面垂直反作用力，计算角速度，分析踝关节动态角位移、角速度、垂直作用力与不同高度的相关性。结果 30 cm高度：地勤人员组与跳伞运动员组踝关节角位移分别为25.73°±8.13°、20.05°±12.27°，垂直反作用力分别为（3 372.4±748.6） N、（5 181.5±1 726.2） N，受力时间分别为（0.049±0.015） s、（0.012±0.004） s，缓冲时间分别为（1.397±0.746） s、（1.737±0.451） s，差异均有统计学意义。60 cm高度：地勤人员组与跳伞运动员组踝关节角速度分别为（25.45±15.01） °/s、（16.51±4.18） °/s，垂直反作用力分别为（4 616.0±1124.7） N、（7 119.5±2 307.4） N，受力时间分别为（0.048±0.013） s、（0.015±0.006） s，缓冲时间分别为（0.922±0.347） s、（1.617±0.547） s，差异均有统计学意义。结论 从不同的测试高度跳下，跳伞运动员组的地面垂直反作用力大于地勤人员组，但角速度及角位移小于地勤人员组。对比地勤人员组，跳伞运动员组的受力时间短而缓冲时间更长。

目的 通过模拟高空跳伞着陆训练环境测定不同高度半蹲式跳伞着陆状态下的踝关节角速度、地面垂直反作用力，为预防跳伞着陆踝部损伤提供生物力学依据。方法 募集18名健康志愿者，包括空军地勤人员9名、职业跳伞人员9名。两组受试者身高、体重的差异无统计学意义。受试者分别从30 cm和60 cm高的跳台以半蹲式跳伞着陆并腿姿势跳落到测力台上。高速摄像机记录着陆过程，测定踝关节跖屈角位移及时间、地面垂直反作用力，计算角速度，分析踝关节动态角位移、角速度、垂直作用力与不同高度的相关性。结果 30 cm高度：地勤人员组与跳伞运动员组踝关节角位移分别为25.73°±8.13°、20.05°±12.27°，垂直反作用力分别为（3 372.4±748.6） N、（5 181.5±1 726.2） N，受力时间分别为（0.049±0.015） s、（0.012±0.004） s，缓冲时间分别为（1.397±0.746） s、（1.737±0.451） s，差异均有统计学意义。60 cm高度：地勤人员组与跳伞运动员组踝关节角速度分别为（25.45±15.01） °/s、（16.51±4.18） °/s，垂直反作用力分别为（4 616.0±1124.7） N、（7 119.5±2 307.4） N，受力时间分别为（0.048±0.013） s、（0.015±0.006） s，缓冲时间分别为（0.922±0.347） s、（1.617±0.547） s，差异均有统计学意义。结论 从不同的测试高度跳下，跳伞运动员组的地面垂直反作用力大于地勤人员组，但角速度及角位移小于地勤人员组。对比地勤人员组，跳伞运动员组的受力时间短而缓冲时间更长。

This study aimed to investigate the influence of prophylactic ankle taping on two balance tests (static and dynamic balance) and one jump test, in the push off and the landing phase. Fifteen active young subjects (age: 21.0 +/- 4.4 years) without previous ankle injuries volunteered for the study. Each participant performed three tests in two different situations: with taping and without taping. The tests were a counter movement jump, static balance, and a dynamic posturography test. The tests and conditions were randomly performed. The path of the center of pressures was measured in the balance tests, and the vertical ground reaction forces were recorded during the push-off and landing phases of the counter movement jump. Ankle taping had no influence on balance performance or in the push off phase of the jump. However, the second peak vertical force value during the landing phase of the jump was 12% greater with ankle taping (0.66 BW, 95% CI -0.64 to 1.96). The use of prophylactic ankle taping had no influence on the balance or jump performance of healthy young subjects. In contrast, the taped ankle increased the second peak vertical force value, which could be related to a greater risk of injury produced by the accumulation of repeated impacts in sports where jumps are frequently performed. Key pointsAnkle taping has no influence on balance performance.Ankle taping does not impair performance during the push-off phase of the jump.Ankle taping could increase the risk of injury during landings by increasing peak forces.

BACKGROUND: Ankle injuries account for 30 to 60% of all parachuting injuries. This study was designed to determine if outside-the-boot ankle braces could reduce ankle sprains during Army paratrooper training. METHODS: The randomized trial involved 777 volunteers from the U.S. Army Airborne School, Fort Benning, Ga. Of this group, 745 completed all study requirements (369 brace-wearers and 376 non-brace-wearers). Each volunteer made five parachute jumps, for a total of 3,674 jumps. RESULTS: The incidence of inversion ankle sprains was 1.9% in non-brace-wearers and 0.3% in brace-wearers (risk ratio, 6.9; p = 0.04). Other injuries appeared unaffected by the brace. Overall, 5.3% of the non-brace group and 4.6% of the brace group experienced at least one injury. The risk ratio for injured individuals was 1.2:1 (non-brace to brace groups; p = 0.65). CONCLUSION: Inversion ankle sprains during parachute training can be significantly reduced by using an outside-the-boot ankle brace, with no increase in risk for other injuries.

This article is a literature review of the aspects of military parachuting related to occupational medicine and focuses on 'conventional' military static line parachuting using a round parachute. The analysis of injuries resulting from military parachuting provide an excellent example of military occupational medicine practice. The techniques of military parachuting are described in order to illustrate the potential mechanisms of injury, and a number of 'classical' parachuting injuries are described. Finally some recommendations are made for the recording of parachute injuries which would assist in the international comparison of injury rates and anatomical distribution.

Long-term spaceflights induce bone loss as a result of profound modifications of bone remodeling, the modalities of which remain unknown in humans. We measured intact parathyroid hormone (PTH) and serum calcium; for bone formation, serum concentrations of bone alkaline phosphatase (BAP), intact osteocalcin (iBGP), and type 1 procollagen propeptide (PICP); for resorption, urinary concentrations (normalized by creatinine) of procollagen C-telopeptide (CTX), free and bound deoxypyridinoline (F and B D-Pyr), and Pyr in a 36-year-old cosmonaut (RTO), before (days -180, -60, and -15), during (from days 10 to 178, n = 12), and after (days +7, +15, +25, and +90) a 180-day spaceflight, in another cosmonaut (ASW) before and after the flight. Flight PTH tended to decrease by 48% and postflight PTH increased by 98%. During the flight, BAP, iBGP, and PICP decreased by 27%, 38%, and 28% respectively in CM1, and increased by 54%, 35%, and 78% after the flight. F D-Pyr and CTX increased by 54% and 78% during the flight and decreased by 29% and 40% after the flight, respectively. We showed for the first time in humans that microgravity induced an uncoupling of bone remodeling between formation and resorption that could account for bone loss.

The mass and architecture of the skeletal system adapt, to some extent, to their mechanical environment. A site-specific bone loss of 1-2% is observed in astronauts and in-flight animals after 1 month of spaceflight. Biochemical data of astronauts and histomorphometric analysis of rat bones show that the change in bone mass is a result of decreased bone formation in association with normal (or increased) bone resorption. The changes in bone formation appear to be due in part to decreased osteoblast differentiation, matrix maturation, and mineralization. Recent data show that spaceflight alters the mRNA level for several bone-specific proteins in rat bone, suggesting that the characteristics of osteoblasts are altered during spaceflight. A possible underlying mechanism is that osteoblasts themselves are sensitive to altered gravity levels as suggested by several studies investigating the effect of microgravity on osteoblasts in vitro. Changes in cell and nuclear morphology were observed as well as alterations in the expression of growth factors (interleukin-6 and insulin-like growth factor binding proteins) and matrix proteins (collagen type I and osteocalcin). Taken together, this altered cellular function in combination with differences in local or systemic factors may mediate the effects of spaceflight on bone physiology.

Spaceflight leads to osteopenia in both humans and animals, principally as a result of decreased bone formation, which might be the consequence of impaired osteoblast differentiation. The effect of microgravity on osteoblast differentiation in vitro was investigated using the human osteosarcoma cell line MG-63. Genes related to matrix formation and maturation were quantified both at the protein and mRNA level in untreated and hormone-treated (dihydroxyvitamin D3 [1,25(OH)2D3], 10(-7) M; transforming growth factor beta2 (TGF-beta2), 10 ng/ml) cells cultured for 9 days under microgravity conditions aboard the Foton 10 satellite and compared with ground and inflight unit-gravity cultures. The expression of alkaline phosphatase (ALP) activity following treatment at microgravity increased only by a factor of 1.8 compared with the 3.8-fold increase at unit-gravity (p < 0.01), whereas no alteration was detected in the production of collagen type I between unit- and microgravity. In addition, gene expression for collagen Ialpha1, ALP, and osteocalcin following treatment at microgravity was reduced to 51, 62, and 19%, respectively, of unit-gravity levels (p < 0.02). The lack of correlation between collagen type I gene and protein expression induced by microgravity is most likely related to the different kinetics of gene and protein expression observed at unit-gravity: following treatment with 1,25(OH)2D3 and TGF-beta2, collagen Ialpha1 mRNA increased gradually during 72 h, but collagen type I production was already maximal after treatment for 48 h. In conclusion, microgravity decreases the activity of osteoblasts in vitro; in particular the differentiation of osteoblasts in response to systemic hormones and growth factors is reduced by microgravity.

Aviation is a critical component of life in Alaska, connecting communities off the road system across the state. Crash-related fatalities in the state are well understood and many intervention efforts have been aimed at reducing aircraft crashes and resulting fatalities; however, nonfatal injuries among workers who perform aviation-related duties have not been studied in Alaska. This study aimed to characterize hospitalized nonfatal injuries among these workers using data from the Alaska Trauma Registry. During 2000-2013, 28 crash-related and 89 non-crash injuries were identified, spanning various occupational groups. Falls were a major cause of injuries, accounting for over half of non-crash injuries. Based on the study findings, aviation stakeholders should review existing policies and procedures regarding aircraft restraint systems, fall protection, and other injury prevention strategies. To supplement these findings, further study describing injuries that did not result in hospitalization is recommended.

BACKGROUND: Women's field lacrosse is described as a noncontact game relying primarily on rules to decrease the risk of head injuries. Despite not allowing head contact, however, concussions continue to be reported in women's field lacrosse. PURPOSE: To assess the ability of men's lacrosse helmets to decrease linear and angular acceleration for different striking techniques in women's field lacrosse. STUDY DESIGN: Controlled laboratory study. METHODS: A helmeted and unhelmeted Hybrid III 50th Percentile headform was attached to a Hybrid III neckform and were subjected to impacts by 8 striking techniques. Eleven athletic females completed 5 slashing techniques, while physical reconstruction equipment was used to simulate falls and shoulder and ball impacts to the head. Three trials were conducted for each condition, and peak resultant linear and angular accelerations of the headform were measured. RESULTS: Falls produced the highest linear and angular acceleration, followed by ball and high-velocity stick impacts. Low-velocity stick impacts were found to produce the lowest linear and angular accelerations. Men's lacrosse helmets significantly decreased linear and angular accelerations in all conditions, while unhelmeted impacts were associated with high accelerations. CONCLUSION: If women's field lacrosse is played within the rules, only falls were found to produce high linear and angular acceleration. However, ball and high-velocity stick impacts were found to produce high linear and angular accelerations. These linear and angular accelerations were found to be within the ranges reported for concussion. When the game is not played within the rules, men's lacrosse helmets provide an effective method of reducing linear and angular accelerations. Thus, women's field lacrosse may be able to reduce the occurrence of high linear and angular acceleration impacts by having governing bodies improving rules, implementing the use of helmets, or both. CLINICAL RELEVANCE: Identifying striking techniques that produce high linear and angular acceleration specific to women's lacrosse and measuring the capacity of a men's lacrosse helmet to reduce linear and angular acceleration.

The bone mineral density and the biochemical parameters exploring bone cell activities were analyzed in two cosmonauts who spent 1 and 6 months, respectively, in the Russian MIR station. Measurements were performed before the flight, after the flight, and after a recovery period. At the end of the first month, peripheral QCT measurements indicated a slight decrease of trabecular bone mass in the distal tibial metaphysis. However, after 6 months of spaceflight, a more marked loss of trabecular and cortical bones was observed in the tibia, and was still significant after 6 month recovery in the trabecular compartment, whereas a decrease was no longer observed in the cortical envelope. No change was observed in either compartment of the distal radius at any time. Ultrasound BUA of the calcaneus was greatly reduced by the first month, followed by a more dramatic decrease after month 6. Ultrasound SOS detected no change. Parameters reflecting bone formation activity appeared to be depressed after both missions. In contrast, no dramatic change in resorption parameters was observed, except for a trend toward an increase in pyridinoline. In conclusion, the lower weight-bearing bones appeared more sensitive than the upper ones in terms of spaceflight-induced bone loss. This probably explained the absence of marked systemic biochemical data changes. This study further suggests that recovery in the tibial trabecular compartment 6 months after landing was not completed after a 6 month mission.

Our laboratories are examining injuries and deaths resulting from mechanical forces applied to aircrew members in the course of Department of Defense aviation operations. In this paper we report only on bodily injuries sustained during ejection from US Air force, aircraft for the fiscal years 1981-1996, that is, major injuries and fatalities resulting directly from seat acceleration forces, from aerodynamic forces applied to crew members during escape through the effects of windblast and parachute opening shock; from direct contact: and from parachute landing injuries. Such injuries occur typically to the head, neck, cervical spine, thorax, thoracolumbar spine, ribs, pelvis, and the upper and lower extremities. Injuries are usually caused by anomalies in the ejection sequence or by delaying ejection until too close to the ground. Conversely, a planned ejection in a modern ejection seat in controlled, low speed flight imposes forces well below injury thresholds. In the USAF, 10-50 aircrew eject yearly, with a decline since 1991. We conclude that the risk of fatality is 0-11% and of major injury is 2-25%. Both are remarkably low and decreasing in the later years of this study period. The absolute number of head, neck, and spine injuries is 0-10 yearly and similarly decreasing. The results of this study are intended to provide a basis for estimating potential savings in deaths, injuries, and costs expected from the development of improved protective measures.

OBJECTIVE: To evaluate whether improvement of proprioception, pain, or dynamic knee instability mediates the effect of wearing a soft knee brace on activity limitations in patients with knee osteoarthritis (OA). METHODS: We conducted an analysis of data for 44 patients with knee OA who were enrolled in a laboratory-based trial evaluating the effect of wearing a commercially available soft knee brace. Activity limitations were assessed with the 10-meter walk test and the Get Up and Go test. Knee joint proprioception was assessed by an active joint position sense test; pain was assessed on a numeric rating scale (NRS) (range 0-10); pressure pain threshold (PPT) was assessed with a hand-held pressure algometer; dynamic knee instability was expressed by the perturbation response, i.e., a measure reflecting a deviation in mean knee varus-valgus angle after a controlled mechanical perturbation on a treadmill, with respect to level walking. Mediation analysis was conducted using the product of coefficients approach. Confidence intervals were calculated with a bootstrap procedure. RESULTS: A decrease in pain (scored on an NRS) and a decrease in dynamic knee instability mediated the effect of wearing a soft knee brace on the reduction of activity limitations (P < 0.05), while changes in proprioception and PPT did not mediate this effect (P > 0.05). CONCLUSION: This study shows that decreased pain and reduced dynamic knee instability are pathways by which wearing a soft knee brace decreases activity limitations in patients with knee OA.

CONTEXT: Long-term effects of ankle bracing on lower extremity kinematics and kinetics are unknown. Ankle motion restriction may negatively affect the body's ability to attenuate ground reaction forces (GRFs). OBJECTIVE: To evaluate the immediate and long-term effects of ankle bracing on lower extremity kinematics and GRFs during a jump landing. DESIGN: Experimental mixed model (2 [group] x 2 [brace] x 2 [time]) with repeated measures. SETTING: Sports medicine research laboratory. PATIENTS OR OTHER PARTICIPANTS: A total of 37 healthy subjects were assigned randomly to either the intervention (n = 11 men, 8 women; age = 19.63 +/- 0.72 years, height = 176.05 +/- 10.58 cm, mass = 71.50 +/- 13.15 kg) or control group (n = 11 men, 7 women; age = 19.94 +/- 1.44 years, height = 179.15 +/- 8.81 cm, mass = 74.10 +/- 10.33 kg). INTERVENTION(S): The intervention group wore braces on both ankles and the control group did not wear braces during all recreational activities for an 8-week period. MAIN OUTCOME MEASURE(S): Initial ground contact angles, maximum joint angles, time to reach maximum joint angles, and joint range of motion for sagittal-plane knee and ankle motion were measured during a jump-landing task. Peak vertical GRF and the time to reach peak vertical GRF were assessed also. RESULTS: While participants were wearing the brace, ankle plantar flexion at initial ground contact (brace = 35 degrees +/- 13 degrees , no brace = 38 degrees +/- 15 degrees , P = .024), maximum dorsiflexion (brace = 21 degrees +/- 7 degrees , no brace = 22 degrees +/- 6 degrees , P = .04), dorsiflexion range of motion (brace = 56 degrees +/- 14 degrees , no brace = 59 degrees +/- 16 degrees , P = .001), and knee flexion range of motion (brace = 79 degrees +/- 16 degrees , no brace = 82 degrees +/- 16 degrees , P = .036) decreased, whereas knee flexion at initial ground contact increased (brace = 12 degrees +/- 9 degrees , no brace = 9 degrees +/- 9 degrees , P = .0001). Wearing the brace for 8 weeks did not affect any of the outcome measures, and the brace caused no changes in vertical GRFs (P > .05). CONCLUSIONS: Although ankle sagittal-plane motion was restricted with the brace, knee flexion upon landing increased and peak vertical GRF did not change. The type of lace-up brace used in this study appeared to restrict ankle motion without increasing knee extension or vertical GRFs and without changing kinematics or kinetics over time.

INTRODUCTION: Modern super agile fighter aircraft are capable of producing an increasing multiaxial acceleration environment which can adversely affect the pilot. An evaluation of the performance of the restraint system during flight maneuvers will benefit restraint designs and, thus, the safety of pilots. METHODS: A finite element model of a mannequin with PCU-15/P harness restraint was used in this study to investigate how the factors, such as strap material stiffness, friction, and belt tension, affect the performance of restraint systems during impact along the -Gx, -Gy, and -Gz directions. The corresponding maximum displacement of the mannequin's torso was computed. RESULTS: The mannequin moved beyond 74 mm sideways. The change in friction coefficient (FC) from 0.1 to 0.4 decreased the displacement of the lower torso by less than 6.7%. The displacement of the torso decreased as the stiffness of the strap or tension increased. Displacement decreased by 9.3%, 6.0%, and 2.7% for the lower torso under the Gx impact, as the tightening force increased from 20 N to 80 N gradually. However, this changed slightly when the stiffness arrived at 1 E or the tension increased to 60 N. DISCUSSION: PCU-15/P harness has the poorest performance during side impact and friction plays an unimportant role in affecting its performance. The stiffness of the webbing used in the PCU-15/P harness is sufficiently high. The lap belt has more effect on limiting the movement of the pilot than the shoulder straps, and a tension of 60 N during the adjustment may be enough for conventional flight maneuvers.

In this prospective study, the parachuting injuries which occurred during 2031 jumps in basic courses of free fall were compared with the injuries occurring during 2468 jumps for reserve paratroopers on training exercises. Fifty-eight injuries were recorded in 51 paratroopers. The ankle was most commonly affected, and 80 per cent of the injuries involved the lower extremity. Only 14 per cent of the injured troopers suffered severe injuries (fractures, knee ligament ruptures). The injury rate for paratroopers on basic courses (19.7 injuries per 1000 jumps) was significantly higher (P < 0.0001) than for those on training exercises (4.5 injuries per 1000 jumps). Similar observations were made for severe injuries (2.0 versus 1.2 injuries per 1000 jumps, respectively). The injury risk increased with age. Most of the injuries occurred on landing, and about 70 per cent were mainly caused by improper landing fall technique. The rate of serious parachuting injuries was low for Norwegian paratroopers.

This article presents the effects of the frontal and rear-end impact loadings on the cervical spine components by using a multi-body dynamic model of the head and neck, and a viscoelastic finite element (FE) model of the six cervical intervertebral discs. A three-dimensional multi-body model of the human head and neck is used to simulate 15 g frontal and 8.5 g rear-end impacts. The load history at each intervertebral joint from the predictions of the multi-body model is used as dynamic loading boundary conditions for the FE model of the intervertebral discs. The results from the multi-body model simulations, such as the intervertebral disc loadings in the form of compressive, tensile, and shear forces and moments, and from the FE analysis such as the von Mises stresses in the intervertebral discs are analysed. This study shows that the proposed approach that uses dynamic loading conditions from the multi-body model as input to the FE model has the potential to investigate the kinetics and the kinematics of the cervical spine and its components together with the biomechanical response of the intervertebral discs under the complex dynamic loading history.

Previous studies have reported the effect of removing the nucleus on biomechanical responses of the human spine to static loadings. However, few studies have dealt with the whole-body vibration condition. The purpose of this study was to investigate the effect of a single-level (L4-L5) nucleus removal on vibration characteristics of the whole lumbar spine in the presence of a physiologic compressive preload, and also to evaluate the preload effect on the vibration characteristics. A 3-D non-linear finite element model of the lumbar spine (L1 to sacrum) subjected to the physiologic conditions of a compressive follower preload was developed and validated. Comparative studies on forced vibration responses between the intact and denucleated models were conducted. The results from the forced-vibration (transient dynamic) analyses considering axial cyclic loading indicated that the nucleus removal increased the dynamic responses at all disc levels. For example, at the denucleated L4-L5 level, after nucleus removal the maximum response values of disc bulge and von-Mises stress in annulus increased by 63.9% and 110.5% respectively, and their vibration amplitudes increased by 97.9% and 139.7% respectively. At other levels, the predicted maximum response values and vibration amplitudes of the stresses and strains also produced 3.1-7.5% and 10.8-30.6% increases respectively due to the nucleus removal, and a relatively larger increase was observed at level L5-S1. It was also found that increasing the preload increased the stresses and strains at all levels but decreased their vibration amplitudes. Nucleus removal at a single level deteriorates the effects of vibration on whole lumbar spine. Also, increasing the preload alters vibration characteristics of the spine. These findings may be useful to provide a guideline for the patients suffering from lumbar disc degeneration to minimize the risk of further injury and discomfort.

OBJECTIVES: To investigate the effect of bracing and taping on selected electromyographic, kinematic, and kinetic variables when landing from a jump. METHODS: Fifteen netball players performed a jump, so as to land on their dominant limb on a force plate. Electromyographic activity was recorded from the gastrocnemius, tibialis anterior, and peroneus longus muscles. Subjects were also filmed and measures of rearfoot motion were derived. RESULTS: Significantly less electromyographic activity (p<0.007) was observed from the gastrocnemius and peroneus longus muscle groups when subjects were braced. No other significant electromyographical findings were observed. Peak vertical ground reaction force and time to peak for vertical ground reaction force were not affected by bracing and taping, nor were the rearfoot and Achilles tendon angles at foot strike. CONCLUSIONS: The effect of bracing and taping on the selected biomechanics variables associated with landing was specifically limited to a reduction in muscle action, particularly for the braced condition. Netball players can be confident that the biomechanics of their landing patterns will not be altered whether they choose to wear a brace or tape their ankle joints.

Physiological changes in humans during spaceflight upon return to earth have been attributed to systemic adaptation, response to stress, and lack of normal exercise. Studies from the Skylab, SL-3, and D-1 missions have demonstrated that significant physiological alterations are seen in single cell prokaryotes and eukaryotes, as well as in animal tissues. Basic cellular functions such as electrolyte concentration, cell growth rate, glucose utilization, bone formation, response to growth stimulation, and exocytosis are modified in microgravity. Many of the physiological changes seen in humans, vertebrate and simple organisms in spaceflight may originate from dysfunction of basic biological mechanisms caused by microgravity. Aging humans share many of the symptoms seen in astronauts during spaceflight. These include reduced cardiac function, loss of bone and reduced immune response and orthostatic hypotension. It is possible that some of physiological adaptations seen in aging may share common physiological basis with those changes seen in spaceflight. Since microgravity affects prokaryotic and eukaryotic cell function at a subcellular and molecular level, space offers us an opportunity to learn more about basic biological mechanisms which are essential to life.

Space flight is an environmental condition where astronauts can lose up to 19% of weight-bearing bone during long duration missions. We used the MC3T3-E1 osteoblast to investigate bone cell growth in microgravity (10(-6) to 10(-9)g). Osteoblasts were launched on the STS-56 shuttle flight in a quiescent state with 0.5% fetal calf serum (FCS) medium and growth activation was initiated by adding fresh medium with 10% FCS during microgravity exposure. Four days after serum activation, the cells were fixed before return to normal Earth gravity. Ground controls were treated in parallel with the flight samples in identical equipment. On landing, cell number, cell cytoskeleton, glucose utilization, and prostaglandin synthesis in flight (n = 4) and ground controls (n = 4) were examined. The flown osteoblasts grew slowly in microgravity with total cell number significantly reduced (55 +/- 6 vs 141 +/- 8 cells per microscopic field). The cytoskeleton of the flight osteoblasts had a reduced number of stress fibers and a unique abnormal morphology. Nuclei in the ground controls were large and round with punctate Hoechst staining of the DNA nucleosomes. The flight nuclei were 30% smaller than the controls (P < 0.0001) and oblong in shape, with fewer punctate areas. Due to their reduced numbers, the cells activated in microgravity used significantly less glucose than ground controls (80.2 +/- 0.7 vs 50.3 +/- 3.7 mg of glucose/dl remaining in the medium) and had reduced prostaglandin E2 (PGE2) synthesis when compared to controls (57.3 +/- 17 vs 138.3 +/- 41 pmol/ml). Cell viability was normal since, on a per-cell basis, glucose use and prostaglandin synthesis were comparable for flight and ground samples. Taken together, these data suggest that growth activation in microgravity results in reduced growth, causing reduced glucose utilization and reduced prostaglandin synthesis, with significantly altered actin cytoskeleton in osteoblasts.

Bone loss has been repeatedly documented in astronauts after flight, yet little is known about the mechanism of bone loss in space flight. Osteoblasts were activated during space flight in microgravity (microg) with and without a 1 gravity (1 g) field and 24 genes were analyzed for early induction. Induction of proliferating cell nuclear antigen (PCNA), transforming growth factor beta (TGFbeta), cyclo-oxygenase-2 (cox-2), cpla2, osteocalcin (OC), c-myc, fibroblast growth factor-2 (fgf-2), bcl2, bax, and fgf-2 message as well as FGF-2 protein were significantly depressed in microg when compared to ground (gr). Artificial onboard gravity normalized the induction of c-myc, cox-2, TGFbeta, bax, bcl2, and fgf-2 message as well as FGF-2 protein synthesis in spaceflight samples. In normal gravity, FGF-2 induces bcl2 expression; we found that bcl2 expression was significantly reduced in microgravity conditions. Since nuclear shape is known to elongate in the absence of mitogens like FGF-2, we used high-resolution image-based morphometry to characterize changes in osteoblast nuclear architecture under microgravity, 1 g flight, and ground conditions. Besides changes in cell shape (roundish/elliptic), other high-resolution analyses show clear influences of gravity on the inner nuclear structure. These changes occur in the texture, arrangement, and contrast of nuclear particles and mathematical modeling defines the single cell classification of the osteoblasts. Changes in nuclear structure were evident as early as 24 h after exposure to microgravity. This documented alteration in nuclear architecture may be a direct result of decreased expression of autocrine and cell cycle genes, suggesting an inhibition of anabolic response in microg. Life on this planet has evolved in a normal gravity field and these data suggest that gravity plays a significant role in regulation of osteoblast transcription.

Alterations in trabecular bone were observed in growing male Wistar rats after 18.5 days of orbital flight on the COSMOS 1129 biosatellite. Spaceflight induced a decreased mass of mineralized tissue and an increased fat content of the bone marrow in the proximal tibial and humeral metaphyses. The osteoblast population appeared to decline immediately adjacent to the growth cartilage-metaphyseal junction, but osteoclast numbers were unchanged. These results suggested that bone formation may have been inhibited during spaceflight, but resorption remained constant. With the exception of trabecular bone mass in the proximal tibia, the observed skeletal changes returned to normal during a 29-day postflight period.

INTRODUCTION: Despite the large number of U.S. military members who conduct parachuting operations, its inherent safety risks, and the introduction of a new military parachute in 2010, little has been published in the last decade on U.S. military parachute fatalities.METHODS: Parachute fatality investigative records maintained by the U.S. Army Combat Readiness Center were reviewed for U.S. Army fatalities resulting from military parachuting operations from January 1, 2010, through December 31, 2015. De-identified data on cases were collected, including causes, lethal injuries, and demographic, environmental, and missional factors. A descriptive analysis was performed.RESULTS: There were 13 cases which met study inclusion criteria. Most occurred during static-line operations and were jumps from a C-17 aircraft using a T-11 parachute. The two most common assigned accident codes were

BACKGROUND: Both ectopia lentis and retinal injury are common results of blunt ocular trauma. Here, we investigated the incidence and characteristics of retinal breaks associated with ectopia lentis caused by blunt ocular trauma. METHODS: Patients who underwent pars plana vitrectomy to treat traumatic lens subluxation and dislocation were retrospectively reviewed. The incidence, characteristics, and outcomes of retinal breaks were analyzed. RESULTS: Forty-five eyes from 45 patients were included in the study. Seventeen eyes (37.7%) were complicated by retinal breaks or detachment, but only four (8.9%) were identified pre-operation. Our study revealed that retinal breaks were more frequently located at the superior (72.7%) and peripheral (81.8%) retina. All patients achieved anatomic recovery post-surgery. The eyes with and without retinal breaks did not differ significantly with respect to initial or final visual acuity. The final visual outcomes were independently and significantly associated with visual acuity at presentation (P = 0.001). CONCLUSIONS: Retinal breaks occurred in approximately one-third of patients with traumatic ectopia lentis and were difficult to observe pre-operation. Complete ophthalmic evaluation and timely intervention may help achieve favorable outcomes.

CONTEXT: Ankle braces may enhance ankle joint proprioception, which in turn may affect reflexive ankle muscle activity during a perturbation. Despite the common occurrence of plantar-flexion inversion ankle injuries, authors of previous studies of ankle muscle latencies have focused on inversion stresses only. OBJECTIVE: To examine the latency of the peroneus longus (PL), peroneus brevis (PB), and tibialis anterior (TA) muscles in response to various degrees of combined plantar-flexion and inversion stresses in braced and unbraced asymptomatic ankles. DESIGN: Repeated measures. SETTING: University biomechanics laboratory. PATIENTS OR OTHER PARTICIPANTS: Twenty-eight healthy females and 12 healthy males (n = 40: mean age = 23.63 years, range = 19 to 30 years; height = 172.75 +/- 7.96 cm; mass = 65.53 +/- 12.0 kg). INTERVENTION(S): Participants were tested under 2 conditions: wearing and not wearing an Active Ankle T1 brace while dropping from a custom-made platform into 10 degrees , 20 degrees , and 30 degrees of plantar flexion and 30 degrees of inversion. MAIN OUTCOME MEASURE(S): The time between platform drop and the onset of PL, PB, and TA electromyographic activity was measured to determine latencies. We calculated a series of 2-way analyses of variance to determine if latencies were different between the conditions (braced and unbraced) and among the plantar-flexion angles (alpha = .05). RESULTS: No interaction was found between condition and plantar-flexion angle. No significant main effects were found for condition or plantar-flexion angle. Overall means for braced and unbraced conditions were not significantly different for each muscle tested. Overall means for angle for the PL, PB, and TA were not significantly different. CONCLUSIONS: Reflexive activity of the PL, PB, or TA was unaffected by the amount of plantar flexion or by wearing an Active Ankle T1 brace during an unanticipated plantar-flexion inversion perturbation.

INTRODUCTION: Military parachuting has been shown to result in injuries. This investigation systematically reviewed studies examining the influence of the parachute ankle brace (PAB) on injuries during military parachuting and performed a cost-effectiveness analysis. EVIDENCE ACQUISITION: Parachute ankle brace studies were obtained from seven databases, personal contacts, and other sources. Investigations were reviewed if they contained original, quantitative information on PAB use and injuries during parachuting. Meta-analysis was performed using a general variance-based meta-analysis method that calculated summary risk ratios (SRR) and 95% CIs. EVIDENCE SYNTHESIS: Five studies met the review criteria. Compared with PAB users, PAB non-users had a higher risk of ankle injuries (SRR=2.1, 95% CI=1.8-2.5); ankle sprains (SRR=2.1, 95% CI=1.4-3.1); ankle fractures (SRR=1.8, 95% CI=1.1-2.9); and all parachuting injuries combined (SRR=1.2, 95% CI=1.1-1.4). The PAB had little effect on lower body injuries exclusive of the ankle (SRR [no PAB/PAB]=0.9, 95% CI=0.7-1.2). Cost-effectiveness analysis estimated that, for every dollar expended on the PAB, a savings of about $7 to $9 could be achieved in medical and personnel costs. CONCLUSIONS: The PAB reduces ankle injuries by about half and is a cost effective device that should be worn during military airborne operations to reduce injury risk.

OBJECTIVE: To identify and analyze articles in which the authors examined risk factors for soldiers during military static-line airborne operations. DATA SOURCES: We searched for articles in PubMed, the Defense Technical Information Center, reference lists, and other sources using the key words airborne, parachuting, parachutes, paratrooper, injuries, wounds, trauma, and musculoskeletal. STUDY SELECTION: The search identified 17 684 potential studies. Studies were included if they were written in English, involved military static-line parachute operations, recorded injuries directly from events on the landing zone or from safety or medical records, and provided data for quantitative assessment of injury risk factors. A total of 23 studies met the review criteria, and 15 were included in the meta-analysis. DATA EXTRACTION: The summary statistic obtained for each risk factor was the risk ratio, which was the ratio of the injury risk in 1 group to that of another (baseline) group. Where data were sufficient, meta-analyses were performed and heterogeneity and publication bias were assessed. DATA SYNTHESIS: Risk factors for static-line parachuting injuries included night jumps, jumps with extra equipment, higher wind speeds, higher air temperatures, jumps from fixed-wing aircraft rather than balloons or helicopters, jumps onto certain types of terrain, being a female paratrooper, greater body weight, not using the parachute ankle brace, smaller parachute canopies, simultaneous exits from both sides of an aircraft, higher heat index, winds from the rear of the aircraft on exit entanglements, less experience with a particular parachute system, being an enlisted soldier rather than an officer, and jumps involving a greater number of paratroopers. CONCLUSIONS: We analyzed and summarized factors that increased the injury risk for soldiers during military static-line parachute operations. Understanding and considering these factors in risk evaluations may reduce the likelihood of injury during parachuting.

A head injury model consisting of the skull, the CSF, the brain and its partitioning membranes and the neck region is simulated by considering its near actual geometry. Three-dimensional finite-element analysis is carried out to investigate the influence of the partitioning membranes of the brain and the neck in head injury analysis through free-vibration analysis and transient analysis. In free-vibration analysis, the first five modal frequencies are calculated, and in transient analysis intracranial pressure and maximum shear stress in the brain are determined for a given occipital impact load.

It has been suggested that microgravity alters bone metabolism. Evidence for this phenomenon includes the negative calcium balance and decreased bone density in astronauts, as well as, inhibition of bone formation in rats flown for 2 to 3 weeks. However, the specific mechanisms that modulate these changes in microgravity are unknown. The purpose of this study was to clarify the mechanism of microgravity-induced bone demineralization using normal rat osteoblasts obtained from femur marrow cultures. The osteoblasts were cultured for 5 days during a Shuttle-Spacelab flight (STS-65). After collection of the culture medium, the cellular DNA and RNA were fixed on board. Enzyme-immunoassay of the culture medium for prostaglandin E2 (PGE2) indicated that microgravity induced a 4.5- to 136-fold increase in flight samples as compared to the ground control cultures. This increase of PGE2 production was consistent with a 3.3- to 9.5-fold elevation of inducible prostaglandin G/H synthase-2 (PGHS-2) mRNA, quantitated by reverse transcription-polymerase chain reaction (RT-PCR). The mRNA induction for the constitutive isozyme PGHS-1 was less than that for PGHS-2. The interleukin-6 (IL-6) mRNA was also increased (6.4- to 9.3-fold) in microgravity as compared to the ground controls. Since PGE2 and IL-6 are both known to play a role in osteoclast formation and bone resorption, these data provide molecular mechanisms that contribute to our understanding of microgravity-induced alterations in the bone resorption process.

Physiological strain plays an important role in maintaining the normal function and metabolism of bone cells. It is well know that the mineral content of astronauts' bones decreases during spaceflight. Thus, gravity is one of the important factors in the musculoskeletal system. The vector-free horizontal clinostat has been used to simulate conditions of microgravity for examining such effects on cells in culture. We analyzed the effects of simulated microgravity using a horizontal clinostat on cultured osteoblast-like cells (HuO9 cell line). Total cellular protein, which was measured as an indication of cell proliferation, was not significantly inhibited under simulated microgravity conditions. No morphological changes were detected under microgravity conditions by phase-contrast microscopy. However, the alkaline phosphatase (ALP) activity and osteocalcin production of the HuO9 cells decreased significantly under microgravity conditions. Our data indicate that simulated microgravity directly inhibits some differentiation phenotypes and some functions of osteoblasts. On the other hand, the addition of 1,25-dihydroxyvitamin D3 (1,25-(OH)2-D3) increased ALP activity under simulated microgravity conditions, although the total activity of ALP in the cells treated with 1,25-(OH)2-D3 was still lower under simulated microgravity conditions than that in the control cells. However, the cells under simulated microgravity conditions showed a greater enhancement of ALP activity by treatment with 1,25-(OH)2-D3.

The speed and altitude at which modern military aircraft operate are such that escape can only be achieved by some means of forcibly propelling the aircrew clear of the aircraft. The most common method of doing this is by use of an ejection seat. The use of such seats, whilst generally life saving, exposes aircrew to forces that may be at the limits of human tolerance. Each phase of the ejection sequence is associated with characteristic injury patterns and of particular concern is the occurrence of spinal compression fractures, which are caused by the upward acceleration of the ejection seat. Thorough investigation of aircrew who eject is necessary and magnetic resonance imaging of the spines of these aircrew is now becoming mandatory. Aircrew who sustain stable anterior wedge compression fractures usually require no invasive treatment, but are prevented from flying aircraft fitted with ejection seats for 3-4 months.

The objective of the study was to determine the effect of landing surface on plantar kinetics during a half-squat landing. Twenty male elite paratroopers with formal parachute landing training and over 2 years of parachute jumping experience were recruited. The subjects wore parachuting boots in which pressure sensing insoles were placed. Each subject was instructed to jump off a platform with a height of 60 cm, and land on either a hard or soft surface in a half-squat posture. Outcome measures were maximal plantar pressure, time to maximal plantar pressure (T-MPP), and pressure-time integral (PTI) upon landing on 10 plantar regions. Compared to a soft surface, hard surface produced higher maximal plantar pressure in the 1(st) to 4(th) metatarsal and mid-foot regions, but lower maximal plantar pressure in the 5(th) metatarsal region. Shorter T- MPP was found during hard surface landing in the 1(st) and 2(nd) metatarsal and medial rear foot. Landing on a hard surface landing resulted in a lower PTI than a soft surface in the 1(st)phalangeal region. For Chinese paratroopers, specific foot prosthesis should be designed to protect the1(st) to 4(th)metatarsal region for hard surface landing, and the 1(st)phalangeal and 5(th)metatarsal region for soft surface landing. Key PointsUnderstanding plantar kinetics during the half-squat landing used by Chinese paratroopers can assist in the design of protective footwear.Compared to landing on a soft surface, a hard surface produced higher maximal plantar pressure in the 1(st) to 4(th) metatarsal and mid-foot regions, but lower maximal plantar pressure in the 5(th) metatarsal region.A shorter time to maximal plantar pressure was found during a hard surface landing in the 1(st) and 2(nd) metatarsals and medial rear foot.Landing on a hard surface resulted in a lower pressure-time integral than landing on a soft surface in the 1(st) phalangeal region.For Chinese paratroopers, specific foot prosthesis should be designed to protect the 1(st) to 4(th) metatarsal region for a hard surface landing, and the 1(st) phalangeal and 5(th) metatarsal region for a soft surface landing.

Retinal detachment typically occurs when the retina is pulled away from its normal position by blunt trauma. It has been estimated that traumatic retinal detachments account for 10-20% of all detachments. Understanding the mechanism of traumatic retinal detachment is helpful for ophthalmologists to make a more accurate diagnosis before the symptoms develop. A finite element eye model, validated through published data, was used to simulate traumatic retinal detachment. Retinal adhesive force was incorporated into the model using breakable bonded contact. Under BB impact, global deformation was divided into four stages: compression, decompression, overshooting and oscillation. Shockwave propagation in the retina produced high strain in the retina. For an impact speed of 50 m/s, the peak strain of 0.138 in ora serrata exceeded the specified threshold for retinal break. When the eye was decompressed, negative pressure occurred around and anterior to the equator, with a minimum of -663 kPa, leading to retinal detachment. The following relative inertia motions between the retina and its supporting tissue extended the detachment. In addition, the simulations of lower shear modulus of vitreous and increased retinal adhesive force also confirm that the extent of retinal detachment is determined by negative pressure and inertial motion. In conclusion, shockwave and negative pressure contribute to retinal detachment. Shockwave propagation in the retina leads to retinal break, while negative pressure and relative inertial motion could pull the retina away from the supporting tissue. The current work would help understand the basic mechanisms underlying blunt trauma. (C) 2013 Elsevier Ltd.

PURPOSE: To develop a mechanical model with which to investigate the relationship between the crimping morphology of collagen fibrils and the nonlinear mechanical behavior of the cornea. METHODS: Uniaxial tensile experiments were performed with corneal strips to test their mechanical behavior. A constitutive model was constructed based on the Gaussian-distributed morphology of crimped collagen fibrils. The parameters that represent the micro characteristics of collagen fibrils were determined by fitting the experimental data to the constitutive model. Transmission electron microscopy (TEM) was used to visualize the crimping morphology of collagen fibrils in the stroma. A quantitative analysis of fibril crimping degrees in the TEM images was conducted to test the parameters predicted by the constitutive model. RESULTS: The parameters were derived using a fitting method that included the expectation for the distribution of fibril crimping degrees, mu = 1.063; the standard deviation, sigma = 0.0781; the elastic modulus of collagen fibrils, E = 52.74 MPa; and the fibril ultimate strain, epsilonb = 0.1957. TEM images showed a variation of the fibril crimping morphology when the cornea was subjected to different tensile loads. A good agreement was found between the parameters derived by the constitutive model and the data quantified from the TEM images. CONCLUSIONS: The nonlinear mechanical behavior of the cornea is closely correlated with the crimping morphology of collagen fibrils. The findings are expected to guide further research of corneal pathologies related to the abnormal microstructure of collagen fibrils.

Parameters of bone formation and resorption were measured in rats orbited for 19.5 days aboard the Soviet Cosmos 782 biological satellite. The most striking effects were on bone formation. During flight, rats formed significantly less periosteal bone than did control rats on the ground. An arrest line at both the periosteum and the endosteum of flight animals suggest that a complete cessation of bone growth occurred. During a 26-day postflight period, the defect in bone formation was corrected. No significant changes in bone resorption were observed.

PURPOSE: To report a variation of the classical needle revision maneuver with an external marking of the scleral flap, augmented with mitomycin C (MMC) in failed non penetrating deep sclerectomy (NPDS). METHOD: This observational prospective pilot study included five consecutive patients who underwent an MMC needling revision of failed NPDS with the external marking of the scleral flap. All participants underwent a complete ophthalmologic examination and data were collected preoperatively as well as 1 day, 1 week and 1 month after the surgery. The surgical site was also evaluated during the procedure. RESULTS: A significant reduction of IOP and antiglaucomatous medication from preoperative levels was detected at the end of the follow-up period. Regarding the surgical site, we succeed in locating the scleral flap and observing the bleb formation in all cases. No significant subconjunctival bleeding was detected. CONCLUSION: This variation of the classical needling technique seems to improve intrasurgical visualization and reduces complications, which might lead to an improvement in surgical success.

The study of sports injuries has grown with the increase in importance of sport as a leisure-time activity. The origin of many sports injuries is assumed to be mechanical, with the forces and/or stresses acting on one element of the human locomotor system exceeding the critical limits. This article presents some biomechanical considerations on the mechanical aspect of the aetiology, reduction and treatment of sport injuries with special emphasis on the lower extremities. Forces acting on the locomotor system have a magnitude, a point of application and a direction. Both magnitude and geometry (point of application and direction) are important in load analysis. However, the geometrical aspect of externally acting forces is an extremely important aspect, especially with respect to reduction of load in practical situations. Load analysis is usually performed with force transducers and optical instruments in order to quantify magnitude and geometry. Two possible approaches to load analysis are discussed. One approach works with the critical limits of biomaterials. This approach shows that the local stresses for cartilage, tendon and bone are in the order of 10 to 20% of the critical limit for normal daily activities, such as walking. The second approach deals with strategies to reduce load, assuming that it is usually too high in sports activities. The nature of playing surfaces and shoes are revealed as important possibilities for load reduction.

The biomechanical difference between the dominant and non-dominant limb has seldom been studied during double-leg landing. The objective of this study was to evaluate the effectiveness of limb laterality on the ankle kinematics, kinetics and electromyogram (EMG) during drop landing. Sixteen healthy adults were recruited and dropped individually from platforms with three different heights (0.32 m, 0.52 m, and 0.72 m). The ground reaction force, ankle joint kinematics, and surface EMG of tibialis anterior (TA) and lateral gastrocnemius (LG) were measured in both lower extremities. Two-way analysis of variance was used to analyze the effects of laterality and dropping height. The peak angular velocities in dorsiflexion and abduction were significantly higher in the dominant ankle, whereas the pre- and post-landing EMG amplitudes of the TA were significantly higher in the non-dominant limb. Compared with the dominant side, the non-dominant ankle has a more effective protective mechanism in that excessive joint motion is restrained by greater ankle flexor activity. Compared with the non-dominant side, the dominant ankle joint is in greater injury risk during drop landing, and data measured in the dominant limb may produce more conservative conclusions for injury protection or prediction.

Predicting neck response and injury resulting from motor vehicle accidents is essential to improving occupant protection. A detailed human cervical spine finite element model has been developed, with material properties and geometry determined a priori of any validation, for the evaluation of global kinematics and tissue-level response. Model validation was based on flexion/extension response at the segment level, tension response of the whole ligamentous cervical spine, head kinematic response from volunteer frontal impacts, and soft tissue response from cadaveric whole cervical spine frontal impacts. The validation responses were rated as 0.79, assessed using advanced cross-correlation analysis, indicating the model exhibits good biofidelity. The model was then used to evaluate soft tissue response in frontal impact scenarios ranging from 8G to 22G in severity. Disc strains were highest in the C4-C5-C6 segments, and ligament strains were greatest in the ISL and LF ligaments. Both ligament and disc fiber strain levels exceeded the failure tolerances in the 22G case, in agreement with existing data. This study demonstrated that a cervical spine model can be developed at the tissue level and provide accurate biofidelic kinematic and local tissue response, leading to injury prediction in automotive crash scenarios.

A total of 90,000 parachute jumps made during a 1 year period resulted in 615 (0.68%) injuries secondary to jumping. Of these 615 cases, 70 jumpers (0.08%) had 71 skeletal injuries as confirmed by roentgenographic examination. Forty-one (57.7%) of the 71 injuries involved the ankle, and 12 (16.9%) were compression fractures of the thoracolumbar spine. The remaining injuries were distributed as follows: shoulder, six (8.5%); calf, six (8.5%); pelvis, 3 (4.2%); foot, two (2.8%); and thigh, one (1.4%). The various mechanisms leading to these injuries are presented.

Skydiving fatalities are mostly accidental and the result of human errors. However, suicides may be greatly underreported in skydivers. We present the case of a young civilian skydiver who committed suicide by jumping from an altitude of 4000m without activating his chutes. Witnesses reported that the victim had remained in a freefall position until ground impact. Besides an extensive blunt trauma, the autopsy showed an antero-posterior flattening of the body with symmetrical abrasions on its front, which were consistent with a high-energy impact on the ground in a

Since 1992 the Consultative Committee on Road Traffic Fatalities in Victoria (CCRTF) has examined the medical management of patients who died following motor vehicle accidents. Three hundred and fifty-five fatalities with head injury occurring between 1 July, 1992 and 31 December 1997 were assessed by the CCRTF. They represented 79% of the total 449 fatalities examined by the Committee. Following examination of the complete medical records and multidisciplinary discussion, the Committee considered 237 (67%) of the 355 neurotrauma deaths to be non-preventable, 105 (30%) potentially preventable and 13 (4%) preventable. The present analysis excludes the non-preventable deaths in order to focus on preventable factors. Problems identified in the 118 patients pre-hospital included: no intubation; prolonged scene time; and no intravenous access; in 139 emergency room attendances: inappropriate reception including delay in arrival of a consultant, no neurosurgical consultation, no CT scan of the head, inadequate blood gases and oxygen monitoring, inadequate fluid resuscitation, delayed respiratory resuscitation and delayed dispatch to the operating room; in 111 operating room visits: no ICP monitoring, inadequate fluid administration and inappropriate anaesthetic technique; and in 90 intensive care unit admissions: no ICP monitoring. Overall, 1745 individual problems in the various areas of care were identified, of which 1104 (63%) were judged to have contributed to death. Improved delivery and quality of trauma care could reduce the identified problems in emergency services and clinical management. Basic principles of trauma management remain the most important means of reducing morbidity and death following road trauma. The leadership role of the neurosurgeon in neurotrauma care is emphasised.

Space flight experiments and studies carried out in altered gravity environments have revealed that exposure to altered gravity conditions results in (mal)adaptation of cellular function. In the present study, we used a clinostat to generate a vector-averaged gravity environment. We then evaluated the responses of osteoblast-like ROS 17/2.8 cells subsequent to rotation at 50 revolutions per minute (rpm) for 6-24 h. We found that the cells started to detach from the substrate between 12 h and 24 h of rotation in clinostat but not in stationary cultures or after horizontal rotation (the latter serving as a motion control for turbulence, shear forces, and vibrations). At 24 h, 35% of clinorotated cells had detached and the cells underwent apoptotic death as evidenced by DNA fragmentation analysis, terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate-biotin nick end labeling (TUNEL) staining, and flow cytometry with Annexin V staining. The apoptotic death was associated with perinuclear distribution of cell-surface integrin beta1 and disorganization of actin cytoskeleton. These results suggest that vector-averaged gravity causes apoptosis of osteoblasts by altering the organization of the cytoskeleton. We hypothesize that apoptotic death of osteoblasts might play an important role in the pathogenesis of osteoporotic bone loss as observed in actual space flights.

PURPOSE: Recurrence of ankle sprains is common among athletes. Although ankle taping reduces the risk of injury, the mechanism underlying its effectiveness remains unclear. Anecdotal reports suggest a role of the belief among athletes that taping will protect them from injury. That is, taping may have a placebo effect. The purpose of the present study was to determine whether there was a placebo effect with ankle taping in individuals with ankle instability. METHODS: Thirty participants with ankle instability completed a hopping test and a modified star excursion balance test under three conditions: (i) real tape, (ii) placebo tape, and (iii) control (no tape). Participants were blinded to the purpose of the study and were informed that the study aimed to compare two methods of ankle taping referred to as mechanical (real) and proprioceptive (placebo). The order of testing the three conditions and the two functional tests was randomized. RESULTS: There was no significant difference in performance among the three conditions for the hopping test (P = 0.865) or the modified star excursion balance test (P = 0.491). However, a secondary exploratory analysis revealed that participants' perceptions of stability, confidence, and reassurance increased with both real and placebo ankle taping when performing the functional tasks. CONCLUSION: The role of the placebo effect of ankle taping in individuals with ankle instability remains unclear. Clinicians should, therefore, continue to use ankle-taping techniques of known efficacy. They should, however, focus on maximizing patients' beliefs in the efficacy of ankle taping, because its application reassured participants and improved their perceived stability and confidence. The effect of ankle taping on participants' perceptions may contribute to its effectiveness in preventing injury.

OBJECTIVES: To examine the efficacy of an outside-the-boot parachute ankle brace (PAB) in reducing risk of ankle injury to army paratrooper trainees and to identify inadvertent risks associated with PAB use. DESIGN: The authors compared hospitalization rates for ankle, musculoskeletal, and other traumatic injury among 223,172 soldiers trained 1985-2002 in time periods defined by presence/absence of PAB use protocols. Multiple logistic regression analysis estimated adjusted odds ratios (OR) and 95% confidence intervals for injury outcomes, comparing pre and post brace periods to the brace protocol period. SETTING: A research database consisting of training rosters from the US Army Airborne training facility (Fort Benning, GA) occupational, demographic, and hospitalization information. MAIN OUTCOME MEASURES: Injuries were considered training related if they occurred during a five week period starting with first scheduled static line parachute jump and a parachuting cause of injury code appeared in the hospital record. RESULTS: Of 939 parachuting related hospitalizations during the defined risk period, 597 (63.6%) included an ankle injury diagnosis, 198 (21.1%) listed a musculoskeletal (non-ankle) injury, and 69 (7.3%) cited injuries to multiple body parts. Risk of ankle injury hospitalization was higher during both pre-brace (adjusted OR 2.38, 95% CI 1.92 to 2.95) and post-brace (adjusted OR 1.72, 95% CI 1.27 to 2.32) periods compared with the brace protocol period. Odds of musculoskeletal (non-ankle) injury or injury to multiple body parts did not change between the brace and post-brace periods. CONCLUSION: Use of a PAB during airborne training appears to reduce risk of ankle injury without increasing risk of other types of traumatic injury.

A stretch-induced increase of active tension is one of the most important properties of the heart, known as the Frank-Starling law. Although a variation of myofilament Ca(2+) sensitivity with sarcomere length (SL) change was found to be involved, the underlying molecular mechanisms are not fully clarified. Some recent experimental studies indicate that a reduction of the lattice spacing between thin and thick filaments, through the increase of passive tension caused by the sarcomeric protein titin with an increase in SL within the physiological range, promotes formation of force-generating crossbridges (Xbs). However, the mechanism by which the Xb concentration determines the degree of cooperativity for a given SL has so far evaded experimental elucidation. In this simulation study, a novel, rather simple molecular-based cardiac contraction model, appropriate for integration into a ventricular cell model, was designed, being the first model to introduce experimental data on titin-based radial tension to account for the SL-dependent modulation of the interfilament lattice spacing and to include a conformational change of troponin I (TnI). Simulation results for the isometric twitch contraction time course, the length-tension and the force-[Ca(2+)] relationships are comparable to experimental data. A complete potential Frank-Starling mechanism was analyzed by this simulation study. The SL-dependent modulation of the myosin binding rate through titin's passive tension determines the Xb concentration which then alters the degree of positive cooperativity affecting the rate of the TnI conformation change and causing the Hill coefficient to be SL-dependent.

The additional weight of combat and protective equipment carried by soldiers on the battlefield and insufficient adaptations to this weight may increase the risk of musculoskeletal injury. The objective of this study was to determine the effects of the additional weight of equipment on knee kinematics and vertical ground reaction forces (VGRF) during two-legged drop landings. We tested kinematics and VGRF of 70 air assault soldiers performing drop landings with and without wearing the equipment. Maximum knee flexion angles, maximum vertical ground reaction forces, and the time from initial contact to these maximum values all increased with the additional weight of equipment. Proper landing technique, additional weight (perhaps in the form of combat and protective equipment), and eccentric strengthening of the hips and knees should be integrated into soldiers' training to induce musculoskeletal and biomechanical adaptations to reduce the risk of musculoskeletal injury during two-legged drop landing maneuvers.

Bubbles in the ocular tear film have been observed following both dry-chamber, simulated compressed air dives and in-water, recreational compressed air dives. The current paper reports on the formation of tear film bubbles in a breath-hold diver following repeated, extended breath-hold excursions to a maximum depth of -28.5 m. It is believed that this is the first time that ocular tear film bubbles have been reported in breath-hold divers.

Despite decades of animal experiments, data on blast injury to the lung cover only a limited number of circumstances and are in a fragmented form. This paper develops a mathematical model of the chest wall dynamics and the subsequent generation of strong pressure waves within the lung, which have been hypothesized as the mediator of injury. The model has been compared to an extensive database of observed pathologies from animal tests. The incidence of injury and lethality is found to follow a log-normal correlation with the computed total energy in these waves and, when the energy is normalized by the lung volume, the lethality correlation applies to all large animal species. Small animals also correlate with the normalized energy, but at a different value, and it is speculated that structural differences, other than lung volume, may be involved. This relatively simple model allows the potential for blast injury to the lung to be determined from measured or computed pressure traces without additional animal testing. Improved occupational exposure criteria should follow from this methodology.

Even though studies on isolated papillary muscles and cardiomyocytes can be applied to the mechanics of a beating heart, it is not always easy for physicians to relate these findings to clinical medicine. Thus, it is important to extend the studies to intact heart either in simulations or in animal models and even better to validate the results with human subjects. Advances in engineering and computer technology have allowed us to bridge the gap between physiology and mechanics. Cardiomyocyte stress/strain relates to muscle energy expenditure, which dictates oxygen and substrate utilization. Appreciation of this sequential relationship by clinicians will facilitate the logical development and assessment of therapies. Theory of finite element analysis (FEA) can predict cardiac mechanics under normal and pathologic conditions. Imaging studies provide an avenue to relate these predictions indirectly to experimental studies. In this fashion, we can understand the mechanical basis for the micro- and macroanatomical twisting motion of the beating heart. The purposes of this manuscript are: (1) to examine the terms that are traditionally used to describe mechanical stresses and strain within the ventricle, (2) to explore the three-dimensional organization of cardiomyocytes that influences global ventricular function, (3) to apply mechanical measures to both single cardiomyofibrils and the intact ventricle (4) to evaluate mathematical and computer models used to characterize cardiac mechanics, and (5) to outline the clinical methods available to measure ventricular function and relate findings from FEA to pathologic conditions.

In this study, a detailed three-dimensional head-neck (C0-C7) finite element (FE) model developed previously based on the actual geometry of a human cadaver specimen was used. Five simulation analyses were performed to investigate the kinematic responses of the head-neck complex under rear-end, front, side, rear- and front-side impacts. Under rear-end and front impacts, it was predicted that the global and intervertebral rotations of the head-neck in the sagittal plane displayed nearly symmetric curvatures about the frontal plane. The primary sagittal rotational angles of the neck under direct front and rear-end impact conditions were higher than the primary frontal rotational angles under other side impact conditions. The analysis predicted early S-shaped and subsequent C-shaped curvatures of the head-neck complex in the sagittal plane under front and rear-end impact, and in the frontal plane under side impact. The head-neck complex flexed laterally in one direction with peak magnitude of larger than 22 degrees and a duration of about 130 ms before flexing in the opposite direction under both side and rear-side impact, compared to the corresponding values of about 15 degrees and 105 ms under front-side impact. The C0-C7 FE model has reasonably predicted the effects of impact direction in the primary sagittal and frontal segmental motion and curvatures of the head-neck complex under various impact conditions.

INTRODUCTION: Previous studies have shown that human articular chondrocytes in vitro are osmolarity-responsive and increase matrix synthesis under cartilage-specific physiological osmolarity. The effects of increased osmolarity on chondrogenesis of progenitor cells in vitro are largely unknown. We therefore aimed to elucidate whether hyperosmolarity facilitates their chondrogenic differentiation and whether Nfat5 is involved. MATERIALS AND METHODS: ATDC5 cells and human bone marrow stem cells (hBMSCs) were differentiated in the chondrogenic lineage in control and increased osmolarity conditions. Chondrogenic outcome was measured by gene- and protein expression analysis. RNAi was used to determine the role of Nfat5 in chondrogenic differentiation under normal and increased osmolarity. RESULTS: Increasing the osmolarity of differentiation medium with 100mOsm resulted in significantly increased chondrogenic marker expression (Col2a1, Col10a1, Acan, Sox9, Runx2 and GAGs) during chondrogenic differentiation of the two chondroprogenitors, ATDC5 and hBMSCs. Nfat5 knockdown under both control and increased osmolarity affected chondrogenic differentiation and suppressed the osmolarity-induced chondrogenic induction. Knockdown of Nfat5 in early differentiation significantly decreased early Sox9 expression, whereas knockdown of Sox9 in early differentiation did not affect early Nfat5 expression. CONCLUSIONS: Increasing the osmolarity of chondrogenic culture media by 100mOsm significantly increased chondrogenic gene expression during the course of chondrogenic differentiation of progenitor cells. Nfat5 may be involved in regulating chondrogenic differentiation of these cells under both normal and increased osmolarities and might regulate chondrogenic differentiation through influencing early Sox9 expression.

Head injury is a leading cause of morbidity and death in both industrialized and developing countries. It is estimated that brain injuries account for 15% of the burden of fatalities and disabilities, and represent the leading cause of death in young adults. Brain injury may be caused by an impact or a sudden change in the linear and/or angular velocity of the head. However, the woodpecker does not experience any head injury at the high speed of 6-7 m/s with a deceleration of 1000 g when it drums a tree trunk. It is still not known how woodpeckers protect their brain from impact injury. In order to investigate this, two synchronous high-speed video systems were used to observe the pecking process, and the force sensor was used to measure the peck force. The mechanical properties and macro/micro morphological structure in woodpecker's head were investigated using a mechanical testing system and micro-CT scanning. Finite element (FE) models of the woodpecker's head were established to study the dynamic intracranial responses. The result showed that macro/micro morphology of cranial bone and beak can be recognized as a major contributor to non-impact-injuries. This biomechanical analysis makes it possible to visualize events during woodpecker pecking and may inspire new approaches to prevention and treatment of human head injury.

Both finite element models and multi-body models of human head-neck complex had been widely used in neck injuries analysis, as the former could be used to generate detailed stress strain information and the later could generate dynamic responses with high efficiency. Sometimes, detailed stress and strain information were hoped to be obtained more efficiently, but current methods were not effective enough when they were used to analyze responses of human head neck complex to long duration undulate accelerations. In this paper, a two-step procedure for 'parallel' development and 'sequential' usage of a pair of human head neck models was discussed. The pair of models contained a finite element model and a multi-body model, which were developed based on the coupling 'parallel' procedure using the same bio-realistic geometry. After being validated using available data, the pair of human neck models were applied to analyze biomechanical responses of pilot's neck during arrested landing operation according to the 'sequential' procedure, because typical sustained undulate accelerations usually appeared during such processes. The results, including both kinematic and detailed biomechanical responses of human head-neck complex, were obtained with preferable efficiency. This research provided an effective way for biomechanical analysis of human head neck responses to sustained undulate accelerations.

The basic hypotheses used during these investigations were based on the vibration analysis of the head, which demonstrated that the head is not a solid nondeformable body, but a complex structure including deformable elements. Laboratoire des Systemes Biomecanique (LSBM) has recently proposed three mathematical models: a lumped model, a finite element model of the head in its sagittal plane, and a three-dimensional finite element model. These models were validated by their modal behavior and enabled the lesion mechanisms to be distinguished as a function of the spectral characteristics of the shock. The objective of this study is to complete these modal results by temporal analysis of the models by calculating the evolution of the intracranian mechanical parameters under shock conditions. To describe the head's dynamic behavior in the temporal domain, constant energy shocks of variable duration were simulated to evaluate their influence on different quantities as the intracerebral stresses in terms of compression, tensile, and shearing stresses, the relative brain-skull displacement, and the skull deformation. The importance of modal behavior of the head is illustrated by analyzing its temporal response to variable duration impacts, thus exciting very different frequencies. For a triangular shock, the critical duration times are between 10 and 15 x 10(-3) s, which correspond to impacts that excite the first resonance frequency of the head. Taking modal behavior into consideration in developing the finite element model leads to a harmonization of the calculated intracerebral stresses, even for short duration shocks. So, when the head is considered as a complex structure made up of several deformable elements, risk limitation is conditioned by an impact energy reduction for frequencies close to the natural frequencies of the structure. In the time field, the objective will be to avoid a number of impact shapes and durations. Therefore, the aim will not be to dampen the impact at any cost, but to damper it in an

A hypokinetic model has been developed which attempts to simulate the weightlessness experienced during space flight. Male rats (approximately 130 g) were suspended from the model with a head-down tilt for a two-week period. Total mechanical unloading of the hind limbs and partial unloading of the fore limbs occurred. In comparison to pair-fed control rats, the skeletal alterations in the proximal tibial and humeral metaphyses of suspended rats were determined to be a diminished rate of longitudinal bone growth, a reduced mass of mineralized tissue, and an accumulation of marrow fat. Also, suspended rats exhibited decreased numbers of osteoblasts and increased numbers of osteoclasts immediately adjacent to the growth plate-metaphyseal junction at both skeletal sites. Although the reduction in mineralized tissue and the fat accumulation were more marked in the tibia, the skeletal changes in the proximal tibial and humeral metaphyses were generally comparable. The observed abnormalities may be due to mechanical unloading and/or a hypersecretion of corticosteroids.

INTRODUCTION: The objective of the study was to investigate the effects of dropping heights and prophylactic ankle braces on ankle joint biomechanics during half-squat parachute landing from two different heights. METHODS: There were 30 male elite paratroopers with formal parachute landing training and more than 2 yr of parachute jumping experience who were recruited for this study. The subjects tested three different ankle brace conditions (no-brace, elastic brace, semirigid brace). Each subject was instructed to jump off a platform from two different heights of 0.4 m and 0.8 m, and land on a force plate in a half-squat posture. The Vicon 3D motion capture system and force plate were used to record and calculate kinematic and kinetic data. RESULTS: Dropping height had a significant effect on peak vertical ground reaction force (vGRF), maximum ankle angular displacement, and time to vGRF. As compared with the no-brace group, use of an elastic ankle brace significantly reduced peak vGRF by 18.57% and both braces significantly reduced the maximal angular displacements of dorsiflexion. The semirigid brace provided greater restriction against maximal angular displacement of inversion. DISCUSSION: The elastic and semirigid ankle braces both effectively restricted motion stability of the ankle joint in the sagittal plane, and the semirigid ankle brace prevented excessive inversion, although the comfort of this device should be improved overall.Wu D, Zheng C, Wu J, Hu T, Huang R, Wang L, Fan Y. Prophylactic ankle braces and the kinematics and kinetics of half-squat parachute landing. Aerosp Med Hum Perform. 2018; 89(2):141-146.

INTRODUCTION: Knee injuries are common among paratroopers and skydivers during landing maneuvers. The aim of this study was to investigate the effects of dropping height and the use of protective knee braces on parachute landing biomechanics. METHODS: The study cohort consisted of 30 male elite paratroopers with formal parachute landing training and more than 2 yr of parachute jumping experience. Each participant was instructed to jump off a platform at two different heights (40 and 80 cm, respectively) and land on force plates in a half-squat posture. All participants tested three different knee brace conditions (no-brace, elastic brace, and semi-rigid brace) at each height. RESULTS: With an increase in dropping height, peak vertical ground reaction forces (GRF), peak flexion angle, peak flexion angular displacement, peak abduction angle, peak abduction angular displacement, peak extorsion angle, and peak extorsion angular displacement of the knee joint all increased. As compared without the use of a brace, use of an elastic or semi-rigid knee brace significantly reduced peak flexion angle, peak flexion angular displacement, peak abduction angular displacement, and peak extorsion angle, while there were no significant differences in peak vertical GRF or peak extorsion angular displacement. The semi-rigid brace provided the greatest restriction against peak abduction angle (3-6 degrees ). DISCUSSION: The elastic and semi-rigid knee braces both effectively restricted motion stability of the knee joint in the sagittal and coronal planes. The semi-rigid brace had a more marked effect, although the comfort of this device should be improved.Wu D, Zheng C, Wu J, Wang L, Wei X, Wang L. Protective knee braces and the biomechanics of the half-squat parachute landing. Aerosp Med Hum Perform. 2018; 89(1):26-31.

In cases of a severe head injury caused by a fall, coup contusions are either absent or very minor, in contrast to presence of extensive contre-coup damage. In cases of a severe blow to head, however, the reverse occurs, with contre-coup lesions a rarity and coup damage extensive. To investigate this further, head injuries caused by a 'blow' or a 'fall' have been studied, using physical human models of the head and neck, both filled with distilled, degassed water and fixed onto a dummy torso. An impact of a constant magnitude was applied to the midoccipital region in 'blow' and 'fall' experiments, and the acceleration of the head and changes in the intracranial pressure were measured, with the resulting data analyzed by a computer. In both experiments, the peak amplitude of the acceleration pulse were almost the same. Similarly, the intracranial pressure curve at the impact site consisted of a positive pulse that hardly differed, nor did the peak amplitude of that pulse vary significantly. In the 'blow' experiment, however, the intracranial pressure curve at the site opposite the impact consisted of a negative pulse, whereas in the 'fall' experiment, the intracranial pressure recorded at the same area was negative but of a longer duration, with an absolute value that was slightly greater. Our results indicate that an impact to the head triggers a different response in the intracranial space, dependent on whether that impact force was caused by a 'blow' or a 'fall'.

OBJECTIVE: Predicting the risk of falls in advance can benefit the quality of care and potentially reduce mortality and morbidity in the older population. The aim of this study was to construct and validate an electronic health record-based fall risk predictive tool to identify elders at a higher risk of falls. METHODS: The one-year fall prediction model was developed using the machine-learning-based algorithm, XGBoost, and tested on an independent validation cohort. The data were collected from electronic health records (EHR) of Maine from 2016 to 2018, comprising 265,225 older patients (>/=65 years of age). RESULTS: This model attained a validated C-statistic of 0.807, where 50 % of the identified high-risk true positives were confirmed to fall during the first 94 days of next year. The model also captured in advance 58.01 % and 54.93 % of falls that happened within the first 30 and 30-60 days of next year. The identified high-risk patients of fall showed conditions of severe disease comorbidities, an enrichment of fall-increasing cardiovascular and mental medication prescriptions and increased historical clinical utilization, revealing the complexity of the underlying fall etiology. The XGBoost algorithm captured 157 impactful predictors into the final predictive model, where cognitive disorders, abnormalities of gait and balance, Parkinson's disease, fall history and osteoporosis were identified as the top-5 strongest predictors of the future fall event. CONCLUSIONS: By using the EHR data, this risk assessment tool attained an improved discriminative ability and can be immediately deployed in the health system to provide automatic early warnings to older adults with increased fall risk and identify their personalized risk factors to facilitate customized fall interventions.

Space flight-induced bone loss has been attributed to a decrease in osteoblast function, without a significant change in bone resorption. To determine the effect of microgravity (MG) on bone, we used the Rotary Cell Culture System [developed by the National Aeronautics and Space Administration (NASA)] to model MG. Cultured mouse calvariae demonstrated a 3-fold decrease in alkaline phosphatase (ALP) activity and failed to mineralize after 7 d of MG. ALP and osteocalcin gene expression were also decreased. To determine the effects of MG on osteoblastogenesis, we cultured human mesenchymal stem cells (hMSC) on plastic microcarriers, and osteogenic differentiation was induced immediately before the initiation of modeled MG. A marked suppression of hMSC differentiation into osteoblasts was observed because the cells failed to express ALP, collagen 1, and osteonectin. The expression of runt-related transcription factor 2 was also inhibited. Interestingly, we found that peroxisome proliferator-activated receptor gamma (PPARgamma2), which is known to be important for adipocyte differentiation, adipsin, leptin, and glucose transporter-4 are highly expressed in response to MG. These changes were not corrected after 35 d of readaptation to normal gravity. In addition, MG decreased ERK- and increased p38-phosphorylation. These pathways are known to regulate the activity of runt-related transcription factor 2 and PPARgamma2, respectively. Taken together, our findings indicate that modeled MG inhibits the osteoblastic differentiation of hMSC and induces the development of an adipocytic lineage phenotype. This work will increase understanding and aid in the prevention of bone loss, not only in MG but also potentially in age-and disuse-related osteoporosis.

Bone formation and structure have been shown repeatedly to be altered after spaceflight. However, it is not known whether these changes are related to a stress-related altered status of the corticosteroid axis. We investigated the role of corticosteroids on spaceflight-induced effects in rat pelvis and thoracic vertebrae. Thirty-six male Sprague-Dawley rats were assigned to a flight, flight control, or vivarium group (n = 12/group). Bilateral adrenalectomy was performed in six rats per group, the additional six rats undergoing sham surgery. Adrenalectomized (ADX) rats were implanted with corticosteroid pellets. On recovery from spaceflight, thoracic vertebrae and the whole pelvis were removed and processed for biochemistry, histomorphometry, or bone cell culture studies. The 17-day spaceflight resulted in decreased bone volume (BV) in the cotyle area of pelvic bones (-12%; p < 0.05) associated with approximately 50% inhibition of bone formation in the cancellous area of pelvic metaphyses and in thoracic vertebral bodies. The latter effect was associated with a decreased number of endosteal bone cells isolated from the bone surface (BS) in these samples (-42%; p < 0.05). This also was associated with a decreased number of alkaline phosphatase positive (ALP+) endosteal bone cells at 2 days and 4 days of culture, indicating decreased osteoblast precursor cell recruitment. Maintaining basal serum corticosterone levels in flight-ADX rats did not counteract the impaired bone formation in vertebral or pelvic bones. Moreover, the decreased ex vivo number of total and ALP+ endosteal bone cells induced by spaceflight occurred independent of endogenous corticosteroid hormone levels. These results indicate that the microgravity-induced inhibition of bone formation and resulting decreased trabecular bone mass in specific areas of weight-bearing skeleton in growing rats occur independently of endogenous glucocorticoid secretion.

Shock reduction has been well studied in moderate activities such as walking and running. However, there is a clear lack of research concerning shock wave transmission and reduction in more strenuous landing activities. In this study, we examined the impact of shock transmission and reduction in landing activities with varied mechanical demands. Ten active males were recruited for the study. They performed five successful step-off landing trials from each of five heights: 30, 45, 60, 75, and 90 cm. Right sagittal kinematics, ground reaction forces, and acceleration were recorded simultaneously. Impact frequencies were analysed using a discrete Fast Fourier Transform and power spectral density was computed. Increased range of motion for the ankle, knee, and hip joints was observed at higher landing heights. The peaks of the vertical ground reaction force, forehead and tibial accelerations, and eccentric muscle work by lower extremity joints were increased with increased landing heights. The peak head power spectral density was severely attenuated at higher frequencies but the peak tibia power spectral density did not demonstrate this trend. Shock reduction showed increased reduction at higher frequencies, but minimal changes across five landing heights. Unlike the responses observed for walking and running, the shock reduction did not show significant improvement with elevated mechanical demands.