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Paper text:
backward walking has is used in a variety of situations as a form of balance training and 
 as a preventive measure for falling .
studies analyzing the motions involved in backward 
 walking have focused on movements of the joints . among these studies
are those indicating 
 the patterns of movements in the joints is the reverse of forward walking and that the 
 trajectories of motion of the two modes of walking are similar1 .
there are also studies that have indicated that the patterns of 
 movements are different due to differences in the stride and speed of walking2 . however , there are almost no studies that 
 have used kinetic analysis .
positive power indicates energy 
 generation , which is generally related to concentric contractions , while negative power 
 indicates energy absorption , which is related to eccentric contractions3 .
therefore , plantar flexion ( push off ) during forward 
 walking is indicated by a large amount of positive power generated at the ankle .
plantar 
 flexion plays a role in forward propulsive force while walking and contributes to the 
 stability and the initial forward motion of the lower limb prior to the swing phase4 .
ankle power is an important index which 
 provides a deeper understanding of the movements of the ankle , and the objective of this 
 study was to perform kinematic and kinetic analyses of the ankle during both forward and 
 backward walking using three - dimensional motion analysis .
the subjects were 11 healthy adults ( 4 women , 7 men ; average age : 23.84.6  years ; average 
 height 167.58.5  cm ; average weight 59.912.6  kg ) .
the main study objectives and methods 
 were explained to the subjects , and they were informed that their decision whether or not to 
 participate in the study would in no way reflect unfavorably on them .
this study was approved by the ethics committee of heisei college of 
 health sciences .  
the figure represents ankle joint power at the forward walking ( a ) , backward walking 
 ( b ) in the sagittal plane during the standing phase for a subject .
the positive value of 
 the vertical axis represents power generation . the negative value represent power 
 absorption .
workload analysis of positive 
 power ( including the peak positive ankle power ) was performed based on the ankle power 
 curve[h1-h3 ] .
measurements of forward and backward walking motions were made using a vicon nexus 
 three - dimensional motion analysis device ( vicon , 6 cameras , sampling frequency 100  hz ) and 3 
 ground reaction force plates ( sampling frequency 1000  hz ) .
infrared markers 14  mm in 
 diameter were placed on 35 sites using the plug - in - gait full body model ( vicon ) . 

measurements were taken of natural walking ( speed and stride were chosen by the walkers ) 
 both forward and backward .
subjects repeated the walking movements several times until they 
 were able to walk stably .
the analysis segment was the 
 standing phase and the items analyzed were walking time , maximum dorsal flexion of the 
 ankle , maximum angle of plantar flexion , peak ankle power in the sagittal plane ( angular 
 velocityjoint moment = w / kg ) , workload of positive ankle power ( integrated value of 
 positive ankle power ) , and work rate ( workload / time ) .
workload analysis of the segment of plantar flexion ( including the peak positive ankle 
 power ) was performed based on the ankle power curve ( fig . 
 1 ) .
statistical analysis consisted of comparisons using the t - test for each of the items 
 measured during both forward and backward walking .
  the figure represents ankle joint angle at the forward walking ( a ) , backward walking 
 ( b ) in the sagittal plane during the standing phase for a subject .
there were no significant differences between the groups 
 in walking time or plantar flexion / range of motion .
the angle of dorsal flexion was 
 13.74.4 in the forward walking group and 20.85.5 in the backward walking group , 
 indicating that the backward walking group had a significantly higher angle of dorsal 
 flexion ( fig .
ankle power was 3.30.7  w / kg in 
 the forward walking group and 1.70.5  w / kg in the backward walking group , indicating that 
 the backward walking group had a significantly lower ankle power .
workload was 29.77.5  w / kg 
 in the forward walking group and 20.87.1  w / kg in the backward walking group , indicating 
 that the backward walking group had a significantly lower workload .
power was 1.70.3  w / kg 
 in the forward walking group and 0.60.1  w / kg in the backward walking group , indicating that 
 the backward walking group had a significantly lower power .
the present results suggest that the kinetic factors of ankle power and workload were lower 
 during backward walking than in forward walking .
since there were no significant differences 
 in walking times in this study , it is likely that plantar flexion plays only a small role in 
 propulsion .
ankle power during forward walking included both plantar flexion caused by 
 muscles and plantar flexion caused by the non - contractile extensibility ( utilizing elastic 
 energy ) of the achilles tendon acting as a spring5 .
however , the plantar flexion power of the ankle during backward 
 walking was low even when the angle of dorsal flexion prior to plantar flexion was large . 

this indicates that the influence of non - contractile elastic energy on plantar flexion is 
 small .
thus , the propulsive force in backward walking must come from some factor other than 
 the ankle .
possible sources of the propulsive force are compensation through hip power and 
 the center of gravity .
power was significantly lower during backward walking . during forward walking the moment 
 arm of plantar flexion increased as walking continued , but during backward walking it 
 decreased .
in other words , it became increasingly more difficult to exert power to generate 
 propulsion .
these differences suggest that even when the 
 movement patterns are the same , they play different roles in forward and backward walking . 
 through the evaluation of ankle power , we can elucidate the contribution to the propulsive 
 force generated by the ankle joint motion , and it is a very important index for 
 understanding the factors of propulsive force in motion .
i would like to investigate the source of the propulsive force in backward walking in the 
 future .
[ purpose ] the purpose of this study was to perform kinematic and kinetic analyses of the 
 ankle during both forward and backward walking using three - dimensional motion analysis . 
 
 [ subjects ] the subjects were 11 healthy adults . [ methods ] measurements of forward and 
 backward walking motions were taken using a three - dimensional motion analysis device and 3 
 ground reaction force plates . 
 the analysis segment was the standing phase and the items 
 analyzed were walking time , maximum dorsal flexion of the ankle , maximum angle of plantar 
 flexion , peak ankle power in the sagittal plane , workload of the ankle , and work rate . 
 statistical analysis consisted of comparisons using the t - test for each of the items 
 measured during both forward and backward walking . 
 [ results ] the backward walking group 
 had significantly lower ankle power , workload , and work rate . [ conclusion ] the propulsive 
 force in backward walking must come from some factor other than the ankle . the analysis of 
 joint power is an important index for understanding the motion .