The effect of 10 weeks of strength training on the electromyographic response of quadriceps portions

Resumen

This study investigate the effect of 10-week strenght training on the amplitude of the electromyographic (EMG) signal  of vastus medialis, vastus lateralis and rectus Femoris. Twenty three untrained volunteers performed 3-5 sets (3 sets - weeks 1 and 2; 4 series - weeks 3 and 4; 5 series weeks 5 to 10) with 6 repetitions, intensity of 50% of 1 repetition maximum (1RM), 3 min rest between sets and 6 s  repetition duration at the knee extensor exercise. One group (5:1) performed concentric action of 5 s and eccentric  of 1 s and the other  (3:3) performed concentric of 3 s and eccentric of 3 s.  The VM, VL and RF EMG (RMS) activities were recorded in each repetition of the three series at the first training session and the first three series at the last session. The protocol 5:1 led to EMG reduction in all portions, with a greater number of repetitions presenting differences at the VL and RF. VM and RF presented similar results at Group 3:3. It was verified that all the differences occurred in the second half of the series. It was also verified differences in EMG ratios just in group 3:3 and only in VM/VL and VM/RF. These results suggest that the coordination was not affected when equivalent repetitions of series were compared. It was also suggested that these results were influenced by the reduced degrees of freedom of the exercise and the training load progression adopted.