Enabling Ankle Movement in Unilateral Leisure Cycling Prostheses: Joint Kinematics and Power Application to the Pedals

Abstract

Unilateral transtibial prostheses for leisure cycling often cause biomechanical asymmetries due to the lack of ankle movement. This study examined whether introducing ankle mobility via a compression spring could reduce these asymmetries. Two male participants with unilateral transtibial amputations—one traumatic (TA; 186 cm, 98 kg, 43 years old, 10 years prosthesis use) and one congenital (CA; 157 cm, 54 kg, 42 years old, lifelong prosthesis use)—cycled on an ergometer (50 W, 60 rpm) using a prototype prosthesis with three compression springs (soft: 4.26 N/mm, medium: 6.17 N/mm, hard: 13.08 N/mm) and a regular prosthesis condition. Hip, knee, and ankle kinematics were evaluated, and pedal power was assessed using instrumented pedals. The TA participant showed improved power symmetry with the hard spring, while the CA participant exhibited exaggerated knee extension without symmetry improvement. In conclusion, ankle mobility may benefit persons with amputations in specific cases.