The Effect of Unequal Crank Arm Lengths and Cycling-Specific Prostheses for Recreational Riders with a Transtibial Amputation.

Abstract

Purpose: We determined the effects of shorter affected side (AS) crank arm lengths and cycling with two different prostheses on joint and crank power, asymmetry, and net efficiency.

Methods: Twelve participants with a TTA rode at 1.5 W·kg -1 with equal (175 mm) and shorter AS crank arms (160, 165, 170 mm) using a daily-use prosthesis and CSP. We used statistical parametric mapping to determine differences in instantaneous joint and crank power between prostheses and linear mixed-effects models to compare average joint and crank power, asymmetry, and net efficiency.

Results: Shorter AS crank arm lengths reduced the magnitude of peak positive ( P ≤ 0.001) and negative ( P < 0.001) crank power on the AS. Use of a CSP increased the magnitude of peak positive knee power ( P < 0.001) and decreased the magnitude of peak negative crank power ( P < 0.001) on the AS compared with a daily-use prosthesis. Shorter AS crank arm lengths while using a CSP reduced average hip joint ( P = 0.014) and hip transfer ( P = 0.025) power asymmetry from 35% to 20% and 118% to 62%, respectively. However, we found no significant differences in AS average joint or crank power, knee joint or crank power asymmetry, or net efficiency.

Conclusions: Cycling at 1.5 W·kg -1 with unequal crank arm lengths and CSP improves hip joint power and hip transfer power asymmetry but does not alter crank asymmetry or net efficiency for recreational cyclists with a TTA.