Introduction. Movement specificity is a critical training principle. In many athletic events, the ability to out-jump an opposing player is vital to success, and a staple to weight training programs for athletes is the back squat. Jump height increases with a greater force exerted by the legs. Traditionally, people emphasize performing a back squat to a depth where a person's thighs are parallel to the floor, but the deeper the squat, the more difficult it becomes to lift heavier weight. However, when jumping, the athlete doesn't squat to parallel before takeoff, but rather "dips" in a shallow squat before takeoff. PURPOSE. Therefore, the purpose of this study was to investigate whether the depth of a back squat has a direct impact on vertical jump performance. Method. Twenty-three recreationally active subjects were randomly assigned to one of three groups: a dip squat (DS) group, half squat (HS) group, or parallel squat (PS) group. All groups trained two days per week for six-weeks using a program incorporating 4 sets of 8 repetitions at 80%-1RM. Inter-set recovery was set at two minutes. DS (n = 6) subjects performed a squat exercise to 135-degrees of knee flexion, HS (n = 8) subjects performed a back-squat exercise to 90-degrees of knee flexion, and PS (n = 7) subjects performed a squat exercise to a depth where their thighs were parallel with the floor. Pre-and post-testing values were compared using analysis of variance (ANOVA) with Tukey's HSD post-hoc analysis. Significance was set at p < .05. RESULTS. Improvements (in inches) for each group were as follows: DS = 2.1 +/- 2.6 cm (mean and standard dev.), HS 2.54 +/- 3.2 cm, PS 3.6 +/- 2.0 cm. No significant differences were found between the three groups (p = .577). Conclusion and application. The depth of the squat does not appear to be a critical factor in improving vertical jump performance in moderately active individuals. Therefore, the overall benefit of squatting to a parallel depth may provide peripheral benefits to the athlete, while not hindering the potential to improve in the vertical jump.
(C) 2011 National Strength and Conditioning Association