Comparison of the effects of isokinetic and isotonic strength training in team sport athletes: A randomized controlled trial

Abstract

Abstract Background Athletes may benefit from isokinetic training (IK) to improve strength and jump performance. However, previous studies comparing IK methods to isotonic resistance training (IT) have utilized high-repetition protocols and a Dynamometer, which are usually reserved for laboratory testing or rehabilitation settings.Methods This study compared the effects of IK and IT using ≤ 6 repetitions on strength and jump performance in 50 male, team-sport athletes (ages 18–35) during COVID-19 lockdown using the commercially-available TechnoGym BioCircuit Dynamometer. With statistical significance set to p < 0.05, this 4-group randomized parallel study assessed the effects of an 8-week isokinetic at 80°/s (IK80; n = 16) and 25°/s (IK25; n = 12) or isotonic training program (IT; n = 15) compared to a control group (CG; n = 7) on anthropometric measurements, peak torque at 80°/s (PT80) and 25°/s (PT25), one-repetition maximum (1-RM) leg extension, and countermovement (CMJ) and squat jump height.Results BM, FFM, FM, and TC were not different between groups post intervention. Strength increased in IT (PT80: p = 0.006; PT25: p = 0.023; 1-RM: p = 0.001), IK80 (PT80: p = 0.004; PT25: p = 0.021; 1-RM: p = 0.009), and IK25 (PT80: p = 0.042; PT25: p = 0.048; 1-RM: p = 0.009) compared to CG, with no difference between intervention groups (p = 1.000). SJ increased in all intervention groups (IT: +1.5cm, p = 0.036; IK80: +2.7cm, p < 0.001; IK25: +1.9cm, p = 0.021) compared to the CG (CG-IT: p = 0.005; CG-IK80: p = 0.009; CG-IK25: p = 0.004), with difference between groups (all p = 1.000). CMJ improved only in IT (+ 1.4cm, p = 0.035) and IK80 (+ 2.7cm, p < 0.001) with no difference between groups (p = 1.000).Conclusions Low-repetition IK and IT can be effectively used to improve strength and jump performance. However, the efficacy of IK on CMJ depends on training velocity and repetition count, with higher velocity training protocols (80°/s) being more effective for jump performance and lower speeds potentially more useful for improving maximal strength (25°/s).