The appropriate activity of the knee agonist-antagonist muscles is important to resist against abnormal abduction-adduction moments loads around knee joint and reduce the risk of knee injuries. Exercise training has been commonly used as an intervention to improve neuromuscular activity of the synergic and/or agonist-antagonist muscles. However, maximizing the effectiveness of exercise interventions for improving neuromuscular activity between muscle groups has been less investigated. The aim of this study was to investigate the improvement in neuromuscular activity of quadriceps and hamstrings muscles after resistance eccentric training versus concentric training.  

26 male subjects randomly recruited for this controlled laboratory study. Subjects were randomly divided into two groups, eccentric training group (No = 13), and concentric training group (No = 13). Maximal knee extension force and bipolar surface electromyography (EMG) signals from quadriceps and hamstrings muscles were recorded before and after concentric and eccentric strength training. Root mean square (RMS) was computed from raw EMG signals.

Percent increase in maximal voluntary isometric contraction (MIVC) of quadriceps muscle after eccentric training was significantly higher than that after concentric training (P < 0.05). Moreover, eccentric training resulted in a greater increase in RMS of EMG for quadriceps and hamstrings muscles compared to concentric exercise training (P < 0.05).

The higher increase in neuromuscular activities within the quadriceps and hamstring muscles observed after eccentric exercise may indicate that resistance training using eccentric contraction is more effective in improving neuromuscular activity of the agonist and antagonist muscles.