STRENGTH FACTORS RELATED TO MAXIMAL POWER OUTPUT DURING JUMP SQUATS WITH AN OPTIMAL LOAD

Abstract

The relationship between maximum lower body strength, as measured by an estimated 1RM back squat, and power output during jump squats has not yet been quantified. This research is a preliminary attempt to understand how maximum squat strength is associated with peak power output during jump squats with a load that permits optimal power output. PURPOSE: To determine what factors are associated with peak power output during jump squats with an optimal load. METHODS: Fourteen male NCAA Division I collegiate volleyball players (body mass: 87 +/− 12.4kg) completed two testing protocols. The first testing protocol was a 1RM squat testing session. During this session a 7–10 repetition maximum load, on a free weight barbell back squat, was determined. This 7–10 RM was then converted to an estimated 1RM using the Brown equation [1RM = (repetitions × 0.0328 + 0.9849) × weight]. During the second testing session, which occurred 7 days after the first session, sets of two jump squats were used to determine the optimal load for power output. The subjects began performing the jump squats with an unloaded bar and then used progressively heavier weights in subsequent sets until the load that produced the maximum power output was isolated. Vertical ground reaction forces were measured using a force platform (Kistler Quattro Jump, Kistler, Switzerland) mounted under the smith machine in which the subjects performed their jump squats. A linear transducer (Ballistic Measurement System, Innervations, IN, USA) was used to measure bar displacement. This force and velocity data was multiplied together to obtain instantaneous power during the jump squats. A Pearson Correlation test with significance set at 0.05 was used to determine associations among the variables. RESULTS: The mean and standard deviations for the 1RM testing, peak power, and optimal load were 137.7 +/− 25.7 kg, 6795 +/− 1027 W, and 30.2 +/− 3.9 kg respectively. The ratio optimal load/1RM was 22.5 +/− 4.3%. There were no significant correlations found between the estimated 1RM and either peak power or the optimal load at which peak power occurred. There were significant negative correlations between total contact time and 1RM and contact time and peak power during the squat jump. CONCLUSION: These results suggest that there is no direct relationship between 1RM strength measured by the squat and power output in the jump squat. However, 1RM squat strength is inversely related to contact time during the squat jumps.