The effects of plyometric jump training on lower-limb stiffness in healthy individuals: A meta-analytical comparison

PurposeThis study aimed to examine the effects of plyometric jump training (PJT) on lower-limb stiffness.MethodsSystematic searches were conducted in PubMed, Web of Science, and Scopus. Study participants included healthy males and females who undertook a PJT programme isolated from any other training type.ResultsThere was a small effect size (ES) of PJT on lower-limb stiffness (ES = 0.33, 95% confidence interval (95%CI): 0.07–0.60, z = 2.47, p = 0.01). Untrained individuals exhibited a larger ES (ES = 0.46, 95%CI: 0.08–0.84, p = 0.02) than trained individuals (ES = 0.15, 95%CI: ?0.23 to 0.53, p = 0.45). Interventions lasting a greater number of weeks (>7 weeks) had a larger ES (ES = 0.47, 95%CI: 0.06–0.88, p = 0.03) than those lasting fewer weeks (ES = 0.22, 95%CI: ?0.12 to 0.55, p = 0.20). Programmes with ≤2 sessions per week exhibited a larger ES (ES = 0.39, 95%CI: 0.01–0.77, p = 0.04) than programmes that incorporated >2 sessions per week (ES = 0.20, 95%CI: –0.10 to 0.50, p = 0.18). Programmes with <250 jumps per week (ES = 0.50, 95%CI: 0.02–0.97, p = 0.04) showed a larger effect than programmes with 250–500 jumps per week (ES = 0.36, 95%CI: 0.00–0.72, p = 0.05). Programmes with >500 jumps per week had negative effects (ES = –0.22, 95%CI: –1.10 to 0.67, p = 0.63). Programmes with >7.5 jumps per set showed larger effect sizes (ES = 0.55, 95%CI: 0.02–1.08, p = 0.04) than those with <7.5 jumps per set (ES = 0.32, 95%CI: 0.01–0.62, p = 0.04).ConclusionPJT enhances lower-body stiffness, which can be optimised with lower volumes (<250 jumps per week) over a relatively long period of time (>7 weeks).