Abstract
This investigation was designed to determine if relatively small manipulations of squat load and the inclusion of selected morphologic variables might augment the explained variance in vertical jump (VJ) displacement. Fifty-two university students (27 women and 25 men) with weight training experience served as subjects. All were assessed for body fat percentage (BF%), height, body weight (BW), leg length (LL), ankle range of motion, and quadriceps angle (Q-angle). Additionally, subjects performed drop vertical jumps (DVJs) and both countermovement jump (CMJ) squats and static jump (SJ) squats at 20, 30, and 40% of their back squat 1 repetition maximum (1RM). A preliminary analysis revealed that DVJcm for all subjects (28.1 ± 6.64; mean ± SD) was most highly correlated with both CMJ @ 30% 1RM (CMJ30PP) and SJ @ 20% 1RM (SJ20PP) (r = 0.84, p < 0.001). Forced multiple regression was then used to determine which variables contributed to VJ displacement. The greatest variability explained (83%) used a CMJ: DVJcm = 20.311 + (0.008) (CMJ30PP) 2 (0.346) (BW). When the same variables were used to calculate separate gender-based regressions, the explained variance in DVJcm (men = 33.0 ± 5.34 cm; women = 23.4 ± 3.79 cm) was 68% for men and 64% for women. These findings suggest that jump squat peak power at a light load is a good predictor of VJ and that its training-induced augmentation would likely improve VJ. The addition of BW to the equation explained slightly more variability in DVJcm than in BF%. Because excess amounts of either would be an additional load to be moved against gravity (fat in general or skeletal muscle in the upper torso), it follows that relatively high levels of either might be expected to attenuate VJ performance.