THE EFFECT OF BARBELL LOAD ON VERTICAL JUMP LANDING FORCE-TIME CHARACTERISTICS

Loaded vertical jumping is often used to assess neuromuscular function and to identify training loads. However, nothing is known about the force-time characteristics of landing from vertical jumping with a range of different barbell loads, which has implications for performance enhancement and injury prevention. PURPOSE: The aim of this study was to quantify the effect that barbell load has on vertical jump landing force-time characteristics. METHODS: Fifteen strength-trained men (mean ± SD: age 23 ± 2 years, mass 84.9 ± 8.1 kg, height 1.80 ± 0.05 m) provided informed consent to perform two vertical jumps with no additional load (body mass: BM) and with additional barbell loads of 25, 50, 75 and 100% of BM on two force plates, and the highest jumps analysed. Jump impulse was calculated by integrating propulsion net force, and jump height calculated from take off velocity. Landing began when force exceeded 10 N and ended when center of mass displacement was zero. Impact and stabilising landing sub-phases were identified either side of peak impact force. Landing impulse was calculated by integrating landing net force; impact and stabilising impulse were calculated from the respective phase duration; and phase change in velocity calculated by dividing by system mass. Mean net forces were calculated by dividing impulse by time. Jump height and landing data were compared across the 5 loads using 1-way ANOVA and effect sizes (ES) calculated. RESULTS: Results are presented in Table 1. Load increments were significant (16±3%, ES: 1.3-2), and significantly affected jump height (49±19%, ES: 2.5-8.2). Impact peak force was maximised with BM, and was not affected by load (p=0.234, ES: 0.18-0.53). Landing time increased with load (30±14%, ES: -0.39-1.23), but relative impact (26±2%) and stabilising time (74±2%) did not (ES: <0.20). Impact (34±15%, p<0.001, ES: 0.36-1.31) and stabilising (28±13%, ES: 0.74-2.56) phase change in velocity decreased with load, but relative change in velocity did not (impact: 26±2%, stabilising: 74±2%, ES: