Delayed-onset muscle soreness and motor performance of the upper extremity

The purpose of this study was to examine the effects of delayed-onset muscle soreness after a strength-training session on the motor performance of the upper extremities, including the reaction time, speed of movement: tapping speed and coordination. In addition, muscle strength, electromyographic (EMG) activity, creatine kinase (CK) and soreness responses were measured. The study was a randomised cross-over intervention study, where 30 subjects (divided into two groups, A and B performed a 1-h muscle strength-training session of the upper extremities, and the responses were measured 48 h after that. All of the subjects experienced muscle soreness, which was evaluated on a visual analogue scale. The mean value of CK activity was 115 IU(.)l(-1) before training and 1259 IU(.)l(-1) after training (P < 0.001). There were no statistically significant differences in wrist flexion/extension muscle strength or EMG tests in either group. Isometric elbow extension strength decreased by 4% (P < 0.01) in group A, and elbow flexion strength decreased by 6% (P < 0.05) in group B. There were no statistically significant changes in simple reaction time, choice reaction timer or speed of movement or coordination in either group. However, tapping speed decreased by 2% (P < 0.05) in group A and by 6% (P < 0.001) in group B. Based on the results of this study, it seems that the feeling of incompetence to perform fast and accurate movements with sore muscles is mainly a subjective feeling, and it may be that the real effect of muscle soreness on motor performance is quite small, and presumably less than generally assumed.