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Mechanics and Energetics of Cycling with Unilateral Transtibial Amputation: Effects of Prosthetic Effective Leg
Stephen P Allen1, Alena M Grabowski1,2
1Department of Integrative Physiology, University of Colorado Boulder, Boulder, CO.
Introduction:
Cyclists with unilateral transtibial amputation (TTA) exhibit kinematic and kinetic asymmetries between their affected and unaffected sides that may influence efficiency. Altering bicycle geometry such as changing prosthetic effective leg length and/or using a cycling-specific prosthesis (CSP) could reduce asymmetries and improve cycling performance.
Purpose:
We determined the biomechanical and metabolic effects of different prosthetic effective leg lengths with two types of prostheses on lower limb joint kinematics and kinetics, asymmetry, and net efficiency in cyclists with TTA.
Methods:
Twelve participants with TTA rode at 1.5 W kg -1 with their standard prosthetic effective leg length and +5, +10, and +15 mm using a daily-use prosthesis and CSP.
Results:
A prosthetic effective leg length of +15 mm decreased the average knee joint angle by 3° for both prosthesis types ( P = 0.02), but did not alter kinematic or kinetic asymmetries, or net efficiency. However, use of a CSP versus daily-use prosthesis increased average knee joint angle of the affected side by 12.5° and decreased knee angle asymmetry from 11% to 3%. There were no changes to joint or crank power asymmetry, but net efficiency improved from 21.4% using a daily-use prosthesis to 22.3% using a CSP.
Conclusions:
Cyclists with a TTA can increase prosthetic effective leg length in a daily-use prosthesis or CSP up to 15 mm without affecting performance. However, use of a CSP decreases knee angle asymmetry and improves efficiency compared with a daily-use prosthesis. CSPs may shift knee extensor muscles into a more favorable region of the force-length relationship for producing force more economically. These findings can be used to inform bicycle and prosthesis designs that may encourage individuals with a TTA to increase exercise and sport participation.
