Athletes' physical fitness changes after cluster resistance training using a flywheel compared to a <i>traditional</i> barbell

This study compared physical fitness adaptations following 8-weeks of flywheel cluster-set and traditional cluster-set training. Seventy-six amateur male field sport athletes (age: 23.5 ± 3.7 years; height: 1.81 ± 0.08 m; body mass: 83.6 ± 14.4 kg) were randomly assigned to flywheel cluster-set, traditional cluster-set, or a control group. Participants underwent pre- and post-intervention assessments for 20 m sprint speed, countermovement jump (CMJ) height, force, and velocity, change of direction (COD) speed, isometric mid-thigh pull (IMTP), and three-repetition maximum (3RM) strength. Both training groups performed quarter-squat and Romanian deadlift exercises twice weekly (four sets of nine repetitions), in cluster blocks of three repetitions (3x3x3) with 45 s intra-set rest. Flywheel blocks included two submaximal 'momentum repetitions' followed by three maximal efforts. No significant group × time interactions were found between flywheel and traditional cluster-set groups for any measure. Compared to the control group, both intervention groups significantly improved sprint speed (5 m and 20 m), CMJ height and force, COD ability, and 3RM strength (p = 0.024 to < 0.001; ES = 0.20-1.14). Additionally, the flywheel group improved IMTP strength (p = 0.049, ES = 0.25), whereas the traditional group improved CMJ velocity (p = 0.011, ES = 0.26). In conclusion, both training modalities effectively enhanced physical fitness in field sport athletes, with flywheel training favouring isometric-strength and traditional methods favouring jump-velocity adaptations.