Association of Accelerometer-Derived Jump Squat Peak Velocity with Drop Vertical Jump Displacement

Abstract

Peak velocity during jump squats with relatively light loads would be expected to be positively associated with drop vertical jump (DVJ) displacement. A relatively convenient and inexpensive accelerometer-based dynamometer is now available for measuring velocity and other variables during such activities. PURPOSE: To determine the association of DVJ displacement with jump squat peak velocity measured by the aforementioned accelerometer. METHODS: Fifty-two subjects (25 men, 27 women) with a minimum of three months squat training experience were recruited from a university population. All performed a one repetition maximum (1RM) back squat to 90 degrees of knee flexion with an external load ≥ body weight prior to the experimental phase of the investigation. Subjects then practiced all activities to be assessed on two separate occasions. DVJ and jump squat testing was initiated in a counterbalanced sequence within one week of the last practice session and subsequently repeated 48 hrs later. Flight time data for jump displacement determination were collected using a uniaxial force platform channeled through a signal conditioner/amplifier interfaced to a PC via a 12-bit analog-digital converter and sampled at 500 Hz. Datapac 5™ was utilized for data extraction. Data were low-pass filtered (4th order, zero-lag Butterworth) with a cutoff frequency of 30 Hz. Jump squats consisted of two styles, static (SJ) and countermovement (CMJ), and were performed in duplicate using 20, 30, and 40% of each subject's back squat 1RM. Concurrent measures of peak velocity were obtained using triaxial accelerometers directly affixed to each end of the barbell midway between the lateral-most aspect of the shoulder and the thumb side of each hand. Acceleration data were downsampled from 1.5 KHz to 500 Hz by averaging every three data points via proprietary software. Jump squat velocity was then determined via integration. Since reliabilities for peak velocity using these devices have been shown elsewhere to be marginal, the two-day average for all pertinent variables was used in determining bivariate correlations (associations). Data were examined for combined men and women, men only, and women only. RESULTS: When considering all subjects (n≈48), all three loads, and both accelerometers, correlations were negligible to moderate (0.09 to 0.61). For men (n≈23), the correlations were low to moderate (0.28 to 0.57). For women (n≈25), the correlations were negligible to low (−0.02 to −0.30). CONCLUSION: The redundant accelerometer-based systems measured peak velocity output during low-load jump squats that had little association with DVJ performance for combined men and women as well as when women were considered in isolation. The associations of DVJ performance with peak velocity under the conditions used in this study were only slightly greater for men than for women. PRACTICAL APPLICATIONS: Within the constraints of this study, it appears that peak velocity during low-load jump squats has little association with DVJ performance in women and only a slightly greater association in men. Therefore, it appears that peak velocity during jump squats with relatively light loads explains little of the variability in DVJ performance. ACKNOWLEDGMENT: This study was supported in part by Myotest, Inc.