Effects of Combined Strength Training Methods on Jump Performance: A Systematic Review and Meta-analysis of Controlled Studies

Actions of short-duration and maximal -effort, such as jumping, are decisive in sports. Using a combination of training (CT) method may be effective to provide variation in stimulus and to increase the overall training adaptation. However, studies analysing the effects of CT are generally limited by small sample sizes. This problem of underpowered studies may, thus, be resolved by pooling study results in a meta-analysis. The objective of this systematic review with meta -analysis was to examine the effects of plyometrics combined with additional training methods (e.g., strength, speed, change of direction (COD)) on vertical jump (VJ) performance, compared with controls groups (CG). The meta -analysis included peer -reviewed articles that incorporated CT in healthy participants and athletes, a CG, and a measure of jumping (CMJ, SJ, DJ and CMJA). The methodological quality of selected studies was assessed with the Cochrane risk of bias tool. Using the random -effects model, effect sizes (ES; Hedge's g) were calculated for jumping measures using means and SDs from pre- and post-tests for each dependent variable. Thirty-six studies were included, comprising 1,169 participants. CT improved VJ tests, CMJ (ES = 0.63; 95% CI = 0.49 to 0.77; p < 0.001), SJ (ES = 0.77; 95% CI = 0.45 to 1.10; p < 0.001), DJ (ES = 0.46; 95% CI = 0.14 to 0.77; p = 0.005) and CMJA height (ES = 1.01; 95% CI = 0.31 to 1.70; p = 0.005). CT is an effective way to improve VJ height in comparison to CG.