Force Variability and Neural Control Differences in an Upper and Lower Limb Muscle
Abstract
This study examined force and motor unit firing rate variability in the first dorsal interosseous (FDI) and the tibialis anterior (TA), focusing on sex-related differences and physical activity. Isometric contractions in the FDI and TA muscles in 12 males and 12 females were examined using electromyography and custom-built dynamometers. Physical activity was monitored using tri-axial accelerometers over seven days. Findings revealed that females exhibited higher CV (coefficient of variation) of force in the TA than FDI, while males displayed higher force variability in the FDI than the TA. Across all contraction intensities, the FDI showed higher firing rate variability than the TA, with no significant difference of muscle in CV of force. Moderate to strong relationships between activity levels and force variability in both FDI and TA at 10, 20 and 50% maximal voluntary contractions were observed. This study prompts further investigation into the neuromuscular control of force in upper and lower limbs, as well as interactions with sex and physical activity.