Effect Of Squat Depth On Vertical Jump Performance Variables

Abstract

Maximizing vertical jump performance is a critical element to success in many athletic situations. Certain individual kinetic and kinematic variables may have greater contributing roles to vertical jump outcome. Squat depth prior to the initiation of the concentric motion would seem to have an impact on these variables, yet there are limited investigations comparing squat depths and vertical jump performance variables. To determine the effect of squat depth on vertical jump performance variables. Seven recreationally-trained males (Height = 177.9 ± 4.7 cm, Weight = 83.6 ± 10.5 kg) performed static jumps (SJ) and countermovement jumps (CMJ) from six squat depths (0.15 m, 0.30 m, 0.45 m, 0.60 m, 0.75 m and preferred depth) in a randomized order. Subjects held a weightless bar across their upper back attached to two linear position transducers ensuring the bar did not move independently of the body while standing on a force plate. Peak force (PF), impulse (I) and jump height (JH) were measured. Significant differences were found between 0.15 m squat depth and other squat depths (0.30 m, 0.45 m, 0.60 m and 0.75 m) for both the SJ and CMJ for PF, I and JH. SJ PF was significantly higher (p < 0.05) at 0.15m (2683.3 ± 281.5 N) in comparison to 0.30m (2285.3 ± 239.6 N), 0.45m (1992.4 ± 190.3 N), 0.60m (1842.5 ± 181.3 N), 0.75m (1761.9 ± 214.2 N). SJ I was significantly lower at 0.15 m (282.3 ± 53.9 N-s) in comparison to 0.30m (377.8 ± 53.3 N-s), 0.45 m (453.0 ± 41.2 N-s), 0.60 m (526.0 ± 62.5 N-s), 0.75 m (597.3 ± 58.1 N-s). SJ JH was significantly lower at 0.15 m (0.275 ± 0.046 m) in comparison to 0.30 m (0.374 ± 0.074 m), 0.45 m (0.447 ± 0.070 m), 0.60 m (0.477 ± 0.078 m), 0.75 m (0.490 ± 0.070 m). CMJ PF was significantly higher at 0.15 m (3068.9 ± 455.6 N) in comparison to 0.30 m (2389.1 ± 294.7 N), 0.45 m (2082.8 ± 266.1 N), 0.60 m (1912.8 ± 228.0 N), 0.75 m (1709.7 ± 210.5 N). CMJ I was significantly lower at 0.15 m (566.9 ± 96.7 N-s) in comparison to 0.30m (816.4 ± 119.3 N-s), 0.45m (930.3 ± 128.1 N-s), 0.60m (1060.6 ± 137.1 N-s), 0.75 m (1123.9 ± 136.2 N-s). CMJ JH was significantly lower at 0.15 m (0.311 ± 0.064 m) in comparison to 0.30 m (0.444 ± 0.055 m), 0.45 m (0.475 ± 0.053 m), 0.60 m (0.508 ± 0.078 m), 0.75m (0.540 ± 0.060 m). For both SJ and CMJ preferred squat depth occurred at the depth that maximized displacement (SJ-0.443 ± 0.060 m, CMJ-0.533 ± 0.037 m) while minimizing contact time (SJ- 253.7 ± 40.6 ms, CMJ-716.9 ± 97.4 ms). A shallow squat depth resulted in higher PF, lower I, and lower JH than squat depths of 0.30 m and lower. High PF values and low I values did not correspond with increased jump height. To maximize jump height a squat depth of at least 0.30m should be utilized for both CMJ and SJ. When self-selecting squat depth, subjects chose a depth that would produce the highest displacement with the shortest amount of contact time. While a shallow squat depth may decrease the time needed to initiate a jump during competition, the result will be a decrease in jump height. While decreased contact time may be required in competition, if the situation allows for an increased contact time it may result in greater jump height which could influence performance.