The effects of velocity loss thresholds during resistance training on lower-limb performance enhancement: A systematic review with meta-analysis

This study assessed the effects of squat training with different velocity loss (VL) thresholds on squat strength, heavy-load squat velocity (HLSV), light-load squat velocity (LLSV), countermovement jump (CMJ) height, and sprint time (ST). A systematic search of electronic databases was conducted. Meta-analysis was used to examine effects of trainings with different VL thresholds and used meta-regression to examine the interaction effects (correlation) between training effects and VL in different performance-based outcomes. Our systematic search yielded 1017 articles, 13 of which were included in the present study. Meta-analysis revealed that resistance training with both low (0%-20%) and high (30%-45%) VL thresholds improved squat strength, HLSV, LLSV, and CMJ height, but only low VL improved ST (p < 0.05). Training gains for HLSV, LLSV, CMJ (p = 0.088), and ST with low VL were superior to those with high VL (p < 0.05). Meta-regression revealed that CMJ (p = 0.076) and ST (p = 0.010) demonstrated improvements as VL decreased in the range of 0% to 45%. In conclusion, squat resistance training with low (<= 20%) VL provides relatively more effective training stimuli, improving performance in power and speed tasks. Optimal VL ranges may be in the range 10% to 20%, <= 20%, and <= 10% for the HLSV and LLSV, CMJ, and ST, respectively.