Influence of pedal characteristics on pedaling control and neural drive in older adults.

This study was aimed to investigate whether pedal characteristics and age affect pedal position accuracy, fluctuation, and neural drive variability during a position control task. Twelve older (age: 72.8 ± 3.6 years) and twelve young (age: 23.8 ± 4.4 years) adults performed trapezoidal position control tasks involving holding plantar flexor contraction for 10 s with four pedal conditions (regular and pulley types × standard and low forces). Neural drive of the triceps surae muscle was estimated with high-density surface electromyograms and individual motor unit decomposition methods. The central 5 s of the sustained contraction phase was used for analysis. Variabilities of the angle and neural drive are presented by the coefficient of variation. We observed that the angle fluctuation was greater in older than young adults for four pedal conditions (p < 0.05). Regardless of age, using pulley pedals increased angle fluctuation more than regular pedals (p < 0.05). No significant interaction was found for pedal conditions and age in pedal position accuracy, angle fluctuation, or neural output. Our results suggest that older adults have poor control ability to maintain pedal angles, and pulley pedals make it difficult to adjust the pedal angles regardless of age. However, the neural output estimated by the continuously active motor units failed to explain these differences.