Rotational flywheel training in youth female team sport athletes: could inter-repetition movement variability be beneficial?

BACKGROUND: The aim of this study was to analyze the effects of an inter-repetition variable rotational flywheel training program (variable) over standard rotational flywheel training (Standard). METHODS: Twenty-four youth female team-sports players were randomly assigned to both training groups (variable, N.=12; standard, N.=12), which consisted of 1 set of 3 rotational flywheel exercises "10-12 repetitions, biweekly fora period of 6-weeks. The participants included in variable group were instructed to perform the movement randomly in one of the three directions (0 degrees, 45 degrees right, and 45 degrees left). Measurements included reactive strength, jumping, change of direction, and sprinting tests; patellar tendon condition was also assessed. RESULTS: Substantial improvements were found in vertical jump with left leg (16.9%), lateral jump with right leg (13.6%), and patellar condition in left leg (4.1%) for standard group, but also in reactive strength index in right leg landing (33.9%), vertical jump with right (10.1%) and left leg (12.0%) for variable group. A significant interaction effect (group x time) was observed on patellar condition in right leg (F-10.02, P<0.01, eta(2)=0.37), favoring variable group. CONCLUSIONS: Rotational flywheel training programs were beneficial for youth-female team-sports athletes, although the movement variability may play a key role to develop different and specific physical adaptations.