Tailoring the second bout of exercise to individual strength losses after initial muscle-damaging exercise: effects on recovery and damage markers

Background: Interindividual variability in response to standardized eccentric exercise presents a major challenge for load management in both research and applied sports settings. The repeated bout effect (RBE) is known to attenuate symptoms in response to exercise-induced muscle damage (EIMD), but it remains unclear whether an individualization of the RBE based on EIMD-markers can reduce the interindividual variability. Methods : Thirty trained males (25.4 ± 2.8 years) completed two bouts of high-speed eccentric hamstring exercise, separated by 14 days. The volume of the repeated bout was individualized based on the peak torque reductions at 48 hours after the first bout. Absolute (Pitman-Morgan test) and relative (coefficient of variation) variance, as well as mean changes (linear mixed models) of neuromuscular function (peak torque, MVC, jumps), muscle tissue changes (elastography, TMG, Myoton), creatine kinase levels, and soreness were assessed pre- and post-exercise up to 96 hours. Results: The individualized repeated bout resulted in significantly lower absolute and relative variance most prominently after 72 hours, in peak torque ( p = 0.04), MVC ( p = 0.02), CK ( p = 0.04), and soreness ( p < 0.001). Conclusion: Individualizing the repeated bout based on peak torque losses of the initial bout reduced the absolute and relative variance of EIMD. This approach could help with load management and recovery strategies in elite sports settings. Trial registration date: 04/07/2023 Trial registration number: DRKS00031644