***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: UNLABELLED Despite the high incidence of chronic ankle instability ( CAI ) , the underlying neurophysiologic mechanism is unknown . Evidence suggests that both feed-forward and feedback mechanisms may play a role . However , no investigation has examined both control mechanisms during the same movement task in the same cohort of CAI patients . PURPOSE To determine the neuromuscular and biomechanical control alterations present in CAI patients during planned ( feed-forward ) and unplanned ( feedback ) gait termination . METHODS Twenty subjects with CAI and 20 uninjured controls completed planned and unplanned gait termination protocol s. Both tasks began with subjects walking at a self-selected speed across a 12-m walkway . Unplanned gait termination required subjects to stop during r and omly selected trials on two adjacent force plates when cued . Planned gait termination required purpose ful stopping on the force places . Propulsive and braking force magnitude and the dynamic postural stability index were calculated from the result ing ground reaction forces . In addition , muscle activity from the soleus , tibialis anterior , and gluteus medius was collected bilaterally . RESULTS Both maximum propulsive ( CAI = 99.8 + /- 40.8 N , control = 88.6 + /- 33.6 N ) and braking ( CAI = 207.1 + /- 80.9 N , control = 161.6 + /- 62.2 N ) forces were significantly higher in the CAI group . The dynamic postural stability index revealed higher scores in the CAI group ( 0.24 + /- 0.03 ) compared with the control group ( 0.22 + /- 0.03 ) . Muscle activation of the soleus and tibialis anterior differed during unplanned and planned gait termination between groups ( P < 0.05 ) and between the limbs of the CAI group ( P < 0.05 ) . CONCLUSIONS Altered biomechanical strategies during both planned and unplanned gait termination indicate that patients with CAI have alterations in feed-forward neuromuscular control and suggest the presence of feedback neuromuscular control deficits CONTEXT Assessment tools should identify functional limitations associated with functional ankle instability ( FAI ) by discriminating unstable from stable ankles . OBJECTIVE To identify assessment tools that discriminated FAI from stable ankles and determine the most accurate assessment tool for discriminating between FAI and stable ankles . DESIGN Case-control study . SETTING Research laboratory . PATIENTS OR OTHER PARTICIPANTS Fifteen individuals with FAI and 15 healthy individuals ; participants with unilateral FAI reported " giving-way " sensations and ankle sprains , whereas healthy participants did not . INTERVENTION(S ) Participants answered 12 questions on the Ankle Joint Functional Assessment Tool ( AJFAT ) .  They also performed a single-leg jump l and ing , which required them to jump to half their maximum jump height , l and on a single leg , and stabilize quickly on a force plate . MAIN OUTCOME MEASURE(S ) Receiver operating characteristic curves determined cutoff scores for discriminating between ankle groups for AJFAT total score and result ant vector ( RV ) time to stabilization . Accuracy values for discriminating between groups were determined by calculating the area under the receiver operating characteristic curves . RESULTS The cutoff score for discriminating between FAI and stable ankles was > or = 26 ( sensitivity = 1 , specificity = 1 ) and > or = 1.58 seconds ( sensitivity = 0.67 , specificity = 0.73 ) for the AJFAT total score and RV time to stabilization , respectively . The area under the curve for the AJFAT was 1.0 ( asymptotic significance < .05 ) , whereas the RV time to stabilization had an area under the curve of 0.72 ( asymptotic significance < .05 ) . CONCLUSIONS The AJFAT was an excellent assessment tool for discriminating between ankle groups , whereas RV time to stabilization was a fair assessment tool . Although both assessment s discriminated between ankle groups , the AJFAT more accurately discriminated between groups than the RV time to stabilization did . Future research ers should confirm these findings using a prospect i ve research design OBJECTIVE To identify changes in ground reaction force during jump l and ing in subjects with functional instability of the ankle joint . DESIGN Comparison of ground reaction force during jump l and ing between subjects with functional instability and healthy controls . BACKGROUND We have recently demonstrated significantly altered patterns of ankle and knee movement immediately pre- and post-impact in subjects with functional instability compared to healthy controls . We now examine the changes in timing and magnitude of forces sustained by the unstable ankle during jump l and ing . METHODS Fourteen subjects with unstable ankles and 10 age , sex and activity matched controls performed five single leg jumps onto a force platform whilst ground reaction forces were sample d. Timing and magnitudes of forces during the first 150 ms following impact were analysed and compared between groups . RESULTS Lateral and anterior force peaks occurred significantly earlier in subjects with functional instability . Significant differences were seen between groups ' time-averaged vertical , frontal and sagittal components of ground reaction force . These ranged from 5 % ( frontal force ) to 100 % ( vertical force ) of body mass . These changes occur immediately post-impact and too early for reflex correction/modification . CONCLUSIONS The disordered force patterns observed in subjects with functional instability are likely to result in repeated injury due to significant increase in stress on ankle joint structures during jump l and ing . We suggest that they are most likely to result from deficits in feed-forward motor control . RELEVANCE These results identify the potentially injurious nature of the changes in the forces applied to the unstable ankle joint during jump l and ing . The timing of these changes suggests that they are caused by a motor control deficit . Treatment approaches aim ed at retraining feed-forward control of ankle joint movement could succeed in restoring more normal patterns of force absorption and reduce the occurrence of repeated micro-trauma to ankle structures Twenty-seven patients who had a unilateral displaced intra-articular fracture of the calcaneus were managed with a cast instead of with reduction or an operation . The clinical result after a mean of six years ( range , two to ten years ) was excellent in five patients , good in five , fair in seven , and poor in ten . The sixteen patients who were re-examined for this study and for whom the gait was analyzed demonstrated abnormalities in ground-reaction force with regard to vertical force ( F3 ) and temporal force factors ( T2 , T3 , T6 , and T9 ) . Analysis of temporal and distance factors showed a trend toward a decreased proportion of single-limb support on the involved side . Three-dimensional motion analysis of the ankle and hindfoot was performed with electrogoniometers as the subject walked on a level surface , on a 10-degree side-slope , and up and down stairs . Motion was decreased in the sagittal , coronal , and transverse planes during walking on level ground and on a side-sloping surface . Significant decreases in motion in these planes were also seen during walking up and down stairs . Although these patients did not have a subsequent reconstructive operation , most had a residual functional deficit BACKGROUND Chronic ankle instability is a common occurrence after an ankle sprain . Yet , some people ( copers ) possess a mechanism that limits recurrent injury and disability . During gait termination , those with chronic ankle instability exhibit altered feed-forward and feedback control but little is known about alterations in copers . Therefore , the purpose of this investigation was to determine the biomechanical control alterations present in controls , copers , and those with chronic ankle instability during planned and unplanned gait termination . METHODS Twenty subjects with chronic ankle instability , 20 copers , and 20 uninjured controls  completed planned and unplanned gait termination tasks . Unplanned gait termination required subjects to stop , when cued , during r and omly selected trials . Planned gait termination required intended stopping . A total of 10 trials were recorded for each condition . Normalized propulsive and braking force magnitudes and dynamic postural stability indices were calculated and compared among the groups . FINDINGS Normalized maximum braking forces were significantly higher in the chronic ankle instability group ( Mean : 2.82 SD : 0.93N/kg ) , relative to copers ( Mean : 2.59 SD : 0.84N/kg ) and controls ( Mean : 2.51 SD : 0.78N/kg ) . Similarly , the antero-posterior postural stability index revealed higher scores in the chronic ankle instability group ( Mean : 0.15 SD : 0.03 ) compared to the coper ( Mean : 0.14 SD : 0.02 ) and control group ( Mean : 0.14 SD : 0.02 ) . Copers did not differ from controls . INTERPRETATION The findings suggest that the ability of copers to terminate gait in a manner similar to uninjured controls may represent part of the underlying mechanism that limits recurrent injury and disability in copers BACKGROUND Functional instability of the ankle joint may interfere with proper execution of quick cutting movements in sports . Previous studies have provided information regarding the ground reaction force characteristics in such movements in healthy players but no research was found in players with ankle instability . The purpose of this study was to evaluate and compare ground reaction forces in functionally unstable ankles with healthy ones during two cutting movements , the v-cut and the defensive shuffle . METHODS Fifteen male basketball players with self reported unilateral functional instability and 17 matched controls , performed three v-cuts and three defensive shuffles on two synchronised force platforms . Both joints were tested and ground reaction forces analysed by an one-way ANOVA for independent groups to test differences between groups , and paired t-test to examine differences within affected players . FINDINGS Unstable ankles , demonstrated significantly greater first vertical force peak , than contralateral unaffected joints ( P < or = 0.05 ) and lower relative time to peak than controls ( P < or = 0.05 ) , during v-cut movement . No significant differences were seen in variables between groups during lateral shuffling . INTERPRETATION Unstable ankles demonstrated altered patterns of ground reaction forces , with a rapid onset of high vertical force during the first millisecond post-impact , while the medial component was unchanged . Although the increased vertical forces are considered predisposing factors to repeated injury , this finding is likely a neuromuscular response making the ankle joint more stable avoiding excessive inversion forces BACKGROUND Little information is available about gait changes in ankle osteoarthritis and total ankle replacement , and also about  total ankle replacement patients ' rehabilitation in the first year after surgery . METHODS Thirty subjects were included in this study : 15 unilateral post-traumatic ankle osteoarthritis patients and 15 age-/gender-matched control subjects . Patients were followed prospect ively : preoperatively , at 3 , 6 , 9 , and 12 months after total ankle replacement . The clinical -functional level was assessed by the American Orthopaedic Foot and Ankle Society ankle and the Short-Form-36 health survey score . 3D ankle-hindfoot kinematic-kinetic analysis  was performed using a motion analysis and a two-plate force-platform system . Statistics included repeated measures analysis of variances , independent sample and paired Student 's t-tests ( significance alpha=0.05 ) . FINDINGS Compared to normal subjects , ankle osteoarthritis caused significant reduction of the American Orthopaedic Foot and Ankle Society and Short-Form-36 score . In gait analysis , ankle osteoarthritis showed a significant deficiency in six of seven spatiotemporal variables , a decrease of the tri-planar ankle movement , a decrease of the second active maximal vertical and the maximal medial ground reaction force , a reduction of the sagittal and transverse ankle joint moments , a reduction of the ankle joint power . Three months after total ankle replacement surgery patients experienced a worsening of gait . At 12 months follow-up , all spatiotemporal variables were not different from the normal subjects ( full rehabilitation ) ; in six of 11 kinematic and kinetic variables there was a partial rehabilitation . INTERPRETATION This study provides data for the clinical -biomechanical underst and ing of the normal , arthritic , and total ankle replacement treated ankle during walking and the first year of rehabilitation 
    Output:
    
The ' walking ' test showed significant differences in a great variety of pathologies , with the magnitude and timing of the ' second peak vertical force ' as proven relevant parameters .
INTERPRETATION This study provides recommendations concerning the potential of various dynamic tests and force plate parameters as a tool to compare neuromusculoskeletal function between patients with foot and ankle pathology and healthy controls