Relationship Between Decomposition of Surface Electromyography Signals and Force Production: Analyzing Recovery From Intense Exercise.

This study investigated the relationship between neuromuscular (motor unit action potential amplitude [MUAP], firing rate, recruitment threshold), biomechanical (force loss), physiological (skin temperature), and perceptual (delayed onset of muscle soreness) markers following an intense knee exercise protocol. Eleven participants performed 2 maximal isometric and 5 concentric-eccentric knee contractions. Assessments were made immediately postexercise (0 h), at 24 hours and 48 hours after intense knee exercise protocol. Electromyography signal decomposition and skin temperature were measured during the protocol, while delayed onset of muscle soreness was evaluated at 24 and 48 hours. A reduction in force production (isometric, dynamic, and Work) was observed at all postexercise time points. Delayed onset of muscle soreness increased at 24- and 48-hour postexercise compared to Pre-exercise. At 0 hours, a positive, moderate correlation was observed between dynamic force loss and MUAP of the vastus lateralis (VL). Two moderate positive correlations were observed between firing rate of rectus femoris and minimum temperature, and between the recruitment threshold of VL and mean temperature. At 24-hour postexercise, a positive moderate correlation was observed between dynamic peak torque and MUAP of VL. These findings suggest that full recovery of force is not achieved at 48-hour postexercise, with MUAP of VL playing a key role in muscle recovery.