Leg muscles recruitment pattern in soccer players and active individuals during isometric contractions

This study aimed to compare the torque, torque ratio (Hamstrings: Quadriceps - H:Q), electromyographic (EMG) activity and EMG ratio (knee flexors: knee extensors EMG) in soccer players (SG, N = 10) and active subjects (AG, N = 10). Subjects performed three maximal voluntary isometric knee extensions and flexions at 45 degrees and 90 degrees to determine the peak torque and EMG activity. Torque and EMG activity of the knee flexor (biceps femoris [BF] and semitendinosus [ST]) were divided by the torque and EMG activity of the knee extensor (vastuls lateralis [VL] and rectus femoris [RF]) to calculate torque ratios (H:Q) and EMG ratios (BF:VL, BF:RF, ST:VL, ST:RF). The flexion torque was significantly higher for SG (p < 0.05) in 45 degrees and 90 degrees. EMG activity for SG was significantly higher in agonist contractions for VL, RF and ST and significantly lower in antagonist contractions for RF and ST when compared to AG. Torque and EMG ratios were similar between groups and there were good correlations between torque ratio and BF:VL ratio (r = 0.71, p = 0.02) and BF:RF ratio (r = 0.81, p = 0.004) at 45. The EMG results could overestimate the joint balance calculated using torque ratios. Differences in recruitment pattern between soccer players and non-athletes can be related to the training routines and the EMG ratios presents applicable in trained populations.