Effects of Complex, Plyometric, and Traditional Resistance Training on Neuromuscular Performance in Highly Trained Male Soccer Players: A Randomized Controlled Trial

The modality of resistance training (e.g., plyometric training PLYO, traditional resistance training TRT) can specifically affect gains in muscle strength and power measures in soccer players. Further, effects of resistance training modality on neuromuscular performance measures (e.g., electromechanical delay EMD) are inconsistent in non-athletes. To examine the effects of PLYO, TRT, and combined PLYO and TRT (i.e., complex training CT) on muscle strength, power, and EMD in highly trained male soccer players (age: 21.7 ± 1.6 years). Participants were randomly assigned to eight weeks of CT (n = 30), PLYO (n = 28), and TRT (n = 26) in addition to their regular soccer training, or soccer training control condition (n = 29). Pre- and post-measurements comprised tests for maximal eccentric knee flexor and concentric knee extensor peak torque (PT), their functional ratio (FUNC-H/Q), and the corresponding EMD of the knee flexors at three angular velocities (60, 180, and 300°/s). Results showed a significant main effect of group for concentric and eccentric PT (p<.001, 1.67 ≤ d ≤ 3.17). Concentric and eccentric PT were larger for CT, PLYO, and TRT groups compared to control group (CG) with the greatest effects for CT across all angular velocities (p<.001, 0.95 ≤ d ≤ 3.57). Additionally, a significant group effect was identified for FUNC-H/Q at 300°/s (p=.002, d = 0.83) with lower ratios in PLYO and TRT groups but not CT compared with CG (p<.001, -0.94 ≤ d≤-0.83). Further, significant and large-sized group effects for EMD were found at 60, 180, and 300°/s (p<.001, 0.96 ≤ d ≤ 2.89). Post-hoc test showed lower EMD values in CT compared with PLYO, TRT, and CG (p<.001, -2.88 ≤ d≤-0.87). Moreover, EMD was lower in PLYO and TRT compared with CG at 60 and 300°/s (p<.001, -1.84 ≤ d≤-1.10). Complex training, PT, and TRT were effective training modalities in improving neuromuscular performance (i.e., maximal eccentric knee flexor/concentric knee extensor PT, knee flexor EMD) in highly trained soccer players. More specifically, CT appears to be superior in maintaining higher FUNC-H/Q values compared with PLYO and TRT. Trial Registration: This study does not report results related to healthcare interventions using human participants and therefore it was not prospectively registered on a clinical trial registry.