First and Second Step characteristics of Amputee and Able-Bodied Sprinters

PURPOSE: In the sprint events, the first two steps are used to accelerate the center of mass horizontally and vertically. Amputee athletes cannot actively generate energy with their running specific prosthesis. It is likely that sprint acceleration mechanics, including step asymmetry, are altered compared to able-bodied athletes. Therefore, the aim of this study was to investigate spatio-temporal and kinetic variables of amputee compared to able-bodied sprinters.

METHODS: Kinematic and kinetic data of the first and second stance were collected from 15 able-bodied and 7 amputee sprinters (2 unilateral-transfemoral, 4 unilateral-transtibial, 1 bilateral-transtibial) with a motion-capture system (250 Hz) and two force plates (1000 Hz), additionally bilateral asymmetry was quantified and compared between groups.

RESULTS: Compared to able-bodied athletes, amputee athletes demonstrated significantly lower performance values for 5 m and 10 m times. Step length, step velocity, step frequency were decreased and contact times increased. Peak horizontal force and relative change of horizontal velocity were decreased in both stances. Peak vertical force and relative change of vertical velocity were lower for the amputee than able-bodied group during first stance, but significantly higher during second stance. During the first stance able-bodied and amputee sprinters displayed a similar orientation of the ground reaction force vector, which became more vertically orientated in the amputee group during second stance. Amputee sprinters showed significantly greater asymmetry magnitudes for vertical force kinetics compared to able-bodied athletes.

CONCLUSION: The running specific prosthesis does not replicate the function of the biological limb well in the early acceleration phase.