Amputee perception of prosthetic ankle stiffness during locomotion.

Only eight participants were tested, and they had to be at least nine months post-amputation and walk one km on a treadmill over 45 min. The sample was not representative of all lower-limb amputees because of the 90 kg upper weight limit and the 45-minute walking requirement. Three subjects walked at 0.87 m/s instead of 1.0 m/s, and the experiment used a treadmill at steady speed rather than over-ground walking with stops. The foot was worn without a shoe, so real-world shoe compliance could change preferred stiffness and perception. Stiffness was changed only as a coupled dorsiflexion-plantarflexion relationship, not independently. Kinematic data were not representative of the perception task because subjects did not have time to adapt their gait. Some participants needed retraining or had memory difficulties, and perception performance likely depended on learning from the first task. The PLUS-M correlation became significant only after removing Subject 2, so it should be read cautiously.

Funding came from Congressionally Directed Medical Research Programs, American Heart Association, and National Science Foundation.

Do not conclude that adjusting prosthetic ankle stiffness to a patient's preference improves walking stability, comfort, energy use, or function. This study measured how well eight participants perceived stiffness changes, not whether a chosen stiffness produced better clinical outcomes.