Effect of Fitness Level on Time Course of Recovery After Acute Strength and High-Intensity Interval Training

Grammenou, M, Kendall, KL, Wilson, CJ, Porter, T, Laws, SM, and Haff, GG. Effect of fitness level on time course of recovery after acute strength and high-intensity interval training. J Strength Cond Res XX(X): 000-000, 2024-The aim was to investigate time course of recovery after acute bouts of strength (STR) and high-intensity interval training (HIIT). A secondary goal was to assess the influence of total fitness score (TFS), composed of handgrip strength and maximum aerobic power on recovery. Twenty-eight resistance-trained individuals completed 8 testing sessions within a 14- to 17-day period. Subjects performed a testing battery comprising isometric midthigh pull (IMTP), countermovement jump (CMJ), and a modified Wingate test (WINmod) at baseline, immediately after exercise, as well as at 6 and 24 hours after the training sessions. A one-way ANOVA was performed to examine time changes after the training sessions. Subjects were then grouped based on their TFS in high, medium, and low groups. To examine the influence of TFS on time course of recovery, we performed a linear mixed-effects model. Statistical significance was set at p < 0.05. Both training sessions resulted in a significant reduction in peak force (PF) that persisted for up to 6 (p < 0.05) and 24 hours (p < 0.001). The STR session showed immediate and 24-hour postexercise declines in jump height and reactive strength index modified (RSImod) compared with baseline. The low TFS group exhibited a significant RSImod reduction immediately after HIIT (p < 0.001), compared with the medium TFS group (p = 0.0002). In the STR session, the high TFS group displayed an increased eccentric displacement during CMJ 24 hours after exercise compared with baseline (p = 0.033). Overall, subjects with high TFS may be able to recover CMJ performance at the same rate as other TFS groups, despite performing more work.