Can horizontal jump performance using minimal individual differences be used to regulate training load in young soccer players? A randomized controlled trial

This randomized controlled trial compared the effects of training load regulation based on horizontal jump (HJ) performance using minimal individual differences (MID) with a pre-planned neuromuscular training control on physical fitness in young soccer players. Nineteen Brazilian youth players were allocated into a regulated group (RG) and a control group (CG). After a familiarization period, HJ reliability was assessed to determine each player's MID, which was then used to guide the RG's training adjustments over six weeks, while the CG followed a traditional training plan. Performance tests included countermovement jump (CMJ), HJ, sprinting (10–30 m), and maximal running speed in the 30–15 Intermittent Fitness Test (V-IFT), assessed at baseline (T0), mid- (T1), and post-intervention (T2). Internal load was monitored using session rating of perceived exertion (sRPE), acute-sRPE, monotony-sRPE, and strain-sRPE. At baseline, performance levels were similar between groups. The RG showed a significant improvement in HJ at T2 (T2 > T0; p = 0.042, ES = moderate ), while both groups improved in V-IFT at T1 (p < 0.001, ES = moderate-large ) and T2 (p < 0.001, ES = moderate ). The RG presented more total jumps during training than the CG (p = 0.007, ES = large ). In conclusion, regulating training load based on HJ performance and MID approach led to better improvements in HJ distance for the RG compared to traditional training. The findings suggest that coaches and researchers could consider HJ performance-based regulation to adapt and individualize neuromuscular training loads.