Biomechanical analysis of patients with mild Parkinson's disease during indoor cycling training.

Background: Parkinson's disease (PD) is characterized by significant postural instability and gait impairments, yet many individuals with PD can continue cycling even with severe gait dysfunction. While previous research has investigated the preservation of pedaling ability, how individuals with PD regulate and adapt their balance control strategies during cycling remains largely unexplored. This study aims to identify the biomechanical adaptations in cycling balance control employed by individuals with PD and how they differ from those of healthy individuals.

Methods: A total of 39 PD patients and 42 age-matched healthy controls participated in a cycling task using a steerable indoor cycling system that enables sliding and tilting motions, requiring them to actively maintain balance while following a straight-line trajectory. Cycling dynamics were analyzed using a sensor-equipped system designed to capture medio-lateral balance adjustments, including force exertion on the handlebars and saddle, lateral deviations, and pedaling speed.

Results: PD patients exhibited a higher coordination of upper and lower body in the medio-lateral direction (PD: 0.47 ± 0.18 vs. Control: 0.11 ± 0.30, p < 0.001), suggesting a stronger reliance on a leaning strategy for balance control. While PD patients cycled at a significantly lower freely chosen speed (6.49 ± 1.45 km/h vs. 10.28 ± 3.00 km/h, p < 0.001), their bike deviation was lower than that of healthy controls (PD: 17.1 ± 9.9 mm vs. Control: 22.8 ± 11.7 mm, p = 0.019), indicating a more constrained and controlled cycling pattern. Additionally, force distribution patterns and bike speed showed strong correlations with physical function measures, including lower limb strength and gait velocity.

Conclusions: This study identifies distinct cycling balance adaptations in PD, providing insights into how individuals with PD regulate and modify their balance control strategies during cycling. The quantitative metrics derived from this study may offer a basis for future research exploring their potential as biomechanical markers for objective functional assessment and rehabilitation monitoring in PD.