***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
    ***DOCUMENTATION*** 
    ***EXAMPLES*** 
    Input: The movement of the center of mass ( COM ) during human walking has been hypothesized to follow a sinusoidal pattern in the vertical and mediolateral directions . The vertical COM displacement has been shown to increase with velocity , but little is known about the mediolateral movement of the COM . In our evaluation of the mediolateral COM displacement at several walking speeds , 10 normal subjects walked at their self-selected speed and then at 0.7 , 1.0 , 1.2 , and 1.6 m/s in r and om order . We calculated COM location from a 15-segment , full-body kinematic model using segmental analysis . Mediolateral COM displacement was 6.99 + /- 1.34 cm at the slowest walking speed and decreased to 3.85 + /- 1.41 cm at the fastest speed ( p < 0.05 ) . Vertical COM excursion increased from 2.74 + /- 0.52 at the slowest speed to 4.83 + /- 0.92 at the fastest speed ( p < 0.05 ) . The data suggest that the relationship between the vertical and mediolateral COM excursions changes substantially with walking speed . Clinicians who use observational gait analysis to assess walking problems should be aware that even normal individuals show significant mediolateral COM displacement at slow speeds . Excessive vertical COM displacement that is obvious at moderate walking speeds may be masked at slow walking speeds The purpose s of this study were to examine age and gender differences in knee extensor strength , power , and fatigue using open- and closed-chain testing procedures . We tested the hypothesis that specific strength ( strength/unit muscle mass ) would not differ by age , whereas age differences in specific power and fatigue would remain consequent to blunted maximal contractile velocity . Skeletal muscle performance was examined in 28 young ( 26.9 + /- 0.7 yr ) and 24 older ( 63.6 + /- 0.8 yr ) men and women . Assessment s included one-repetition maximum strength for knee extension , leg press , and squat ; concentric knee extensor peak power , velocity , and fatigability ; and  sit-to-st and power , fatigability , and relative neural activation ( electromyograph activity during sit-to-st and movement normalized to electromyograph activity during isometric maximum voluntary contraction ) . Thigh lean mass ( TLM ; kg ) was assessed by dual-energy X-ray absorptiometry . Specific strength ( N/kg TLM ) and specific power ( W/kg TLM ) were estimated by dividing absolute values by TLM . Age differences in specific strength were observed for knee extension only ( young , 41.2 + /- 1.0 N/kg TLM ; older , 32.4 + /- 1.0 N/kg TLM ; P < 0.05 ) . Adjustment for TLM did not negate age differences in knee extension specific power ( 25 - 41 % lower in older ; P < 0.05 ) across loads tested . Older adults experienced fatigue across 10 repetitions of knee extension as peak velocity fell by 24 % ( P < 0.05 ) . Deficits in concentric power persist after adjustment for TLM as maximum contractile velocity falls markedly with aging . Older adults are less capable of sustaining maximum concentric velocity during repetitive contractions . These findings suggest that velocity impairments are a possible contributor to mobility loss and falls risk among older adults . Interventions for improving contractile velocity should be pursued Although much has been learned in recent decades about the deterioration of muscular strength , gait adaptations , and sensory degradation among older adults , little is known about how these intrinsic changes affect biomechanical parameters associated with slip-induced fall accidents . In general , the objective of this laboratory study was to investigate the process of initiation , detection , and recovery of inadvertent slips and falls . We examined the initiation of and recovery from foot slips among three age groups utilizing biomechanical parameters , muscle strength , and sensory measurements . Forty-two young , middle-age , and older participants walked around a walking track at a comfortable pace . Slippery floor surfaces were placed on the track over force platforms at r and om intervals without the participants ' awareness . Results indicated that younger participants slipped as often as the older participants , suggesting that the likelihood of slip initiation is similar across all age groups ; however , older individuals ? recovery process was much slower and less effective . The ability to successfully recover from a slip ( thus preventing a fall ) is believed to be affected by lower extremity muscle strength and sensory degradation among older individuals . Results from this research can help pinpoint possible intervention strategies for improving dynamic equilibrium among older adults STUDY DESIGN A cross-sectional study in patients with recurrent/chronic low back trouble and healthy control subjects . OBJECTIVE To evaluate the effect of paraspinal muscle fatigue on the ability to sense a change in lumbar position . SUMMARY OF BACKGROUND DATA Protection against spinal injury requires proper anticipation of events , appropriate sensation of body position , and reasonable muscular responses . Lumbar fatigue is known to delay lumbar muscle responses to sudden loads . It is not known whether the delay is because of failure in the sensation of position , output of the response , or both . METHODS Altogether , 106 subjects ( 57 patients with low back trouble [ 27 men and 30 women ] and 49 healthy control subjects [ 28 men and 21 women ] ) participated in the study . Their ability to sense a change in lumbar position while seated on a special trunk rotation unit was assessed . A motor rotated the seat with an angular velocity of 1 degree per second . The task in the test involved reacting to the perception of lumbar movement ( rotation ) by releasing a button with a finger movement . The test was performed twice , before and immediately after a fatiguing procedure . During the endurance task , the participants performed upper trunk repetitive extensions against a resistance , with a movement amplitude adjusted between 25 degrees flexion and 5 degrees extension , until exhaustion . RESULTS Patients with chronic low back trouble had significantly poorer ability than control subjects on the average to sense a change in lumbar position ( P = 0.007 ) , which was noticed before and after the fatiguing procedure . Lumbar fatigue induced significant impairment in the sensation of position change ( P < 0.000001 ) . CONCLUSIONS Lumbar fatigue impairs the ability to sense a change in lumbar position . This feature was found in patients and control subjects , but patients with low back trouble had poorer ability to sense a change in lumbar position than control subjects even when they were not fatigued . There seems to be a period after a fatiguing task during which the available information on lumbar position and its changes is inaccurate The contribution of central and peripheral factors to muscle fatigue were quantified following a high-intensity uphill running exercise .  Eight male volunteers performed an intermittent exercise at 120 % of maximal aerobic speed on a treadmill with an 18 % grade . Electrically evoked and voluntary contractions of the knee extensors and EMG of the two vastii were analyzed before and immediately after the high-intensity exercise .  Isometric maximal voluntary contraction decreased slightly ( -7+/-8 % ; p < 0.05 ) after exercise but no changes were found in the level of maximal activation or in the torque produced by a 80 Hz maximal stimulation applied to the femoral nerve . Following exercise , the single twitch was characterized by lower peak torque , maximal rate of force development , and relaxation ( -28+/-11 % , -25+/-12 % , -31+/-15 % respectively , p < 0.001 ) , and higher surface of the M-wave for both vastii . The ratio between the torques evoked by 20 Hz and 80 Hz stimulation declined significantly ( -22+/-10 % , p < 0.01 ) after exercise . These findings indicate that muscle fatigue after high-intensity running exercise is due to significant alteration in excitation-contraction coupling and that this type of exercise does not induce significant central fatigue or changes at the crossbridge level Aims : To determine whether fatigue and need for recovery are risk factors for being injured in an occupational accident . Methods : These associations were investigated within the Maastricht Cohort Study of “ Fatigue at Work ” , a prospect i ve cohort study of employees from a wide range of companies and organisations . For 7051 employees information was available on fatigue as measured with the Checklist Individual Strength ( CIS ) , need for recovery as measured with the VBBA , and possible confounding factors such as age , smoking , alcohol consumption , educational level , shift work , and work environment . Information on the risk factors was collected in May 1999 and January 2000 , before the occurrence of the occupational accidents . The incidence of being injured in an occupational accident was inventoried over the year 2000 . A total of 108 employees reported having been injured in an occupational accident in 2000 . Results : For the highest CIS fatigue score tertile a for age , gender , educational level , smoking , shift work , and work environment , adjusted relative risk for being injured in an occupational accident of 1.29 ( 95 % CI : 1.03 to 2.78 ) was found compared to the lowest tertile , and for the highest tertile of need for recovery a relative risk of 2.28 ( 95 % CI : 1.41 to 3.66 ) was found . Conclusions : Fatigue and need for recovery were found to be independent risk factors for being injured in an occupational accident . This means that in the push back of occupational accidents , fatigue , and even more importantly need for recovery , need special attention 
    Output:
    
Several spatiotemporal parameters were reported to change with fatigue , but the few variables studied in multiple studies , gait speed and stride or step length and stride time , were affected only in single studies .
Fatigue appears to modulate spatiotemporal gait parameters , but the effects of fatigue appear to be dependent on the muscles that were fatigued , and age that appears to be a moderator of the effects of fatigue on gait