Gait termination on declined compared to level surface; contribution of terminating and trailing limb work in...

To terminate gait, the mechanical work-done by the lower-limbs is likely to be predominantly negative but how such work is produced/completed has not previously been investigated. The aim of this study was to determine the amount of negative mechanical (external) work-done by the lower-limbs, along with the associated joints (muscle) work, to terminate gait and how these work contributions were affected by a change in surface angle. Eight males completed terminations on the level floor and a declined ramp. Negative mechanical limb-work (limbW_(-ve)) was computed (each orthogonal direction) as the dot-product of the ground-reaction-force and centre-of-mass (CoM) velocity. Inverse dynamics was used to calculate ankle, knee and hip negative joints (muscle) work (Wj_(-ve)). Measures were determined for each limb for the two-locomotor steps of gait termination. The trailing-limb did 67% (-0.386 J/kg) of the overall limbW_(-ve) to terminate gait on the level; and this increased to 74% (-0.451 J/kg) for ramp trials. Wj_(-ve) was greater for the trailing- (ankle -0.315; knee -0.357; hip -0.054 J/kg) compared to terminating- limb (ankle, -0.063; knee -0.051; hip -0.014 J/kg), with the increases in ankle Wj_(-ve) being temporally associated with increases in perpendicular limbW_(-ve). Wj_(-ve) increased on both limbs for declined compared to level surface, particularly at the knee (declined -0.357, level -0.096 J/kg), with such increases being temporally associated with increases in parallel limbW_(-ve). These findings provide new perspectives on how the limbs do work on the CoM to terminate gait, and may be helpful in designing prosthetic limbs to facilitate walking on ramps.