Bilateral Differences in Leg-spring Behavior in Transtibial Amputee Sprinters

Abstract

An increased understanding of leg-spring behavior in amputee sprinters during bouncing gaits would provide important information that may be used for injury prevention, evaluation of their sprint ability and development of sprint-dedicated prostheses. In the present study, we investigated bilateral differences in leg stiffness during one-legged hopping in amputee sprinters. Three male transtibial amputee sprinters performed one-legged hopping in place, matching metronome beats at 2.2, 2.6, and 3.0 Hz in a randomized order. Amputees hopped both on their sound limb and prosthetic limb, which has energy storage and return properties. Based on a spring-mass model, we calculated leg stiffness, which is defined as the ratio of maximal ground reaction force to maximum center of mass displacement at the middle of the stance phase, using subject’ s body mass, contact time and aerial time. In all hopping frequency settings, bilateral asymmetry in the leg stiffness was about 10%, which was similar to those of able-bodied subjects. Thus, the results of the present study suggest that amputee sprinters have a similar level of bilateral asymmetry in leg stiffness during hopping with inactive non-amputees. However, hopping frequencies where the greatest asymmetry in leg stiffness was observed in each transtibial amputees were dependent on each individual. These results will assist in the formulation of treatment-specific training regimes and rehabilitation programs for amputee sprinters, and the development of sprint-dedicated prostheses taking considerations with residual lime length, stump status, musculoskeletal properties.