Statistical Analyses
For the comparison of adaptations between the groups, we calculated mixed linear models with the outcome of a measurement (e.g., jump height) as the dependent variable and time (PRE vs. post), group (BALANCE vs. HIIT-BALANCE vs. HIIT-BALANCE), and physiological state (fatigued vs. unfatigued) as factors. Separate analyses were calculated for each outcome (shuttle run performance, jump height, sway path while standing on (a) solid ground, (b) balance wobble board, (c) soft mat). Random intercepts and slopes on the individual level were used. This allowed for analyzing different trajectories in the adaptations of postural stability, shuttle run performance, and jump height over time between the groups accounting for individual variation. All estimates of the interaction between time and group are reported together with the corresponding standardized effect size and 95% confidence interval. Thus, the reported estimates can be interpreted as the difference in performance changes between the groups over time. As recommended for longitudinal studies, any training adaptations are also reported using change scores (