The effects of passive and active warm-ups on vertical jump, stretch-shortening cycle and reactive strength index performance

Abstract

Passive warm-up, via hot-water immersion (HWI) for instance, may enhance explosive performance by increasing lower-limb temperature without imposing the metabolic demands associated with exercise. However, it remains unclear whether passive heating influences jump tasks with different concentric and stretch-shortening cycle (SSC) demands and whether its effects are comparable to those achieved following active warm-up (AWU). Hence, this thesis aimed to compare the acute effects of passive warm-up via HWI and AWU, on three different vertical jump performance tasks in physically active adults, including squat jump (SJ), countermovement jump (CMJ), and drop jump (DJ). Twenty participants (15 males and 5 females; age: 25.9 ± 4.5 years) completed the two warm-up conditions and a control condition (CON) via thermoneutral water immersion in a randomised crossover design. Passive warm-up involved 60 min of waist-level HWI at 42°C, whereas CON involved 60 min of immersion at 34°C. AWU comprised 15 min of cycling at a rating of perceived exertion of 14 (6-20 Borg scale), followed by dynamic lower-limb movements, 10 bodyweight squats, and 10 submaximal CMJs. The three vertical jump tests, SJ, CMJ, and DJ were assessed before and immediately after each condition on a force platform. The analysed outcomes were SJ and CMJ height and peak propulsive force (PPF), along with DJ height and reactive strength index (RSI). Change scores (post minus pre) were compared between conditions using analysis of variance (ANOVA) followed by Bonferroni-adjusted post hoc comparisons. Significant condition effects were observed for SJ height (p < .001), SJ PPF (p = .002), CMJ height (p < .001), DJ height (p = .006), and DJ RSI (p < .001). Bonferroni-adjusted comparisons showed that the positive changes observed following HWI differed significantly from the corresponding changes following AWU (SJ height, p < .001; SJ PPF, p = .020; CMJ height, p < .001; DJ height, p = .017; DJ RSI, p = .011) and CON (SJ height, p < .001; SJ PPF, p = .002; CMJ height, p < .001; DJ height, p = .015; DJ RSI, p < .001). CMJ PPF did not differ significantly among conditions (p = .108). These findings demonstrate that 60 min of waist-level HWI at 42°C can acutely improve concentric-dominant jump performance via SJ test and performance in jumps involving slow- and fast-SSC demands via CMJ and DJ, respectively. In addition, the passive warm-up via HWI enhanced RSI during DJ while AWU showed no difference to the CON condition. In conclusion, passive warm-up via 60 min of HWI at 42°C appears to be an effective strategy for acutely enhancing vertical jump performance across tasks characterised by concentric-dominant, slow-SSC, and fast-SSC demands.