Effects of individualised training programmes based on the force-velocity imbalance on physical performance in rugby players

BACKGROUND: The use of force-velocity imbalance (Fvimb) has been proposed as an effective method for prescribing training loads aiming to enhance physical performance. OBJECTIVE: This study aimed to analyse the effects on lower body strength, jump and sprint performance of different individualised resistance training (RT) programmes based on Fvimb in rugby players. METHODS: Thirty-four senior rugby players were divided into four groups according to their Fvimb: Not individualised (NI, n = 8), velocity imbalance (Vimb, n = 6), force imbalance (Fimb, n = 11) and well balanced (WB, n = 9). The intervention period consisted of a 7-week resistance, plyometric and sprint training programme performed twice a week. Pre- and Post-training measures included Force-velocity (Fv) profile, countermovement jump (CMJ), 30 m sprint test and estimated one-repetition maximum in squat (1RM-SQ). RESULTS: Significant "group" x "time" interactions (P < 0.05) were observed for theoretical maximal velocity (V0), theoretical maximal force (F0), and Fvimb. No significant "group" x "time" interactions were observed for the rest of variables analysed. The Vimb group significantly (P < 0.05) increased V0, whereas decreased F0 and Fvimb. The Fimb group showed significant (P < 0.05) decreases in V0, whereas increased F0 and Fvimb. The WB and NI groups did not show significant changes in these parameters. The WB group induced significant enhancements in 10 m, 20 m, and 30 m sprint times, maximum sprint speed and sprint momentum (SM), whereas Fimb attained significant changes in 20 m and 30 m sprint times. The NI group attained significant improvements (P < 0.05) in SM. No significant changes were observed for 1RM-SQ and jump performance. CONCLUSION: Individualised RT programs based on Fvimb induced improvements in sprint performance. Moreover, individualised RT programs based on Fvimb induced better adjustments of the Fv profile to the theoretical "optimal" Fv profile, although any group improved SQ strength, jump height or maximum power.