Beyond Jump Height: Load-Dependent Effects of Lightweight Wearable Resistance on Countermovement and Drop Jump Biomechanics

Of interest were the acute effects of lightweight lower-limb wearable resistance (WR) on the kinematics and kinetics of the countermovement jump (CMJ) and drop jump (DJ). Twenty male athletes (age: 18.05 ± 0.6 years; body mass: 76.4 ± 7.6 kg; height: 182.4 ± 5 cm) performed the CMJ and DJ under four loading conditions: 0%, 2%, 4%, and 6% body mass (BM). Variables of interest included jump height (JH), countermovement depth (CMD), total SSC duration (TCT/GCT), eccentric and concentric phase durations, relative concentric impulse (rCI), relative concentric mean force (rCMF), relative concentric mean power (rCMP), and concentric force index (CFI). Two-way repeated-measures ANOVAs were used to assess jump × load interactions, with Bonferroni-adjusted pairwise comparisons and planned contrasts used to examine within-jump and between-jump load responses, respectively. Significant jump × load interactions were observed for all variables analysed. In the CMJ, JH significantly decreased across all loaded conditions, including an 8.3% reduction with 2% BM. In contrast, DJ JH was preserved at 2% BM but significantly decreased at 4% and 6% BM. However, 2% BM was sufficient to increase DJ GCT and ConT, and reduce rCMF, CFI, and rCMP (p < 0.05). The change in JH differed between jumps at 2% BM only, whereas changes in CMD, rCMF, CFI, and rCMP differed between jumps across all WR loads. It appears that lightweight WR produces distinct jump-specific responses. Greater initial changes in CMJ JH and CMD suggest that WR altered countermovement strategy before substantially impairing concentric force production, whereas in the DJ, WR altered fast SSC force–time variables before reducing JH. When utilising WR to improve JH performance, practitioners should therefore avoid interpreting JH in isolation and monitor temporal variables (GCT/TCT/ConT/EccT), CMD, rCMF, rCMP and CFI.