Reliability Of A Velocity Measuring Device During Four Intensities Of The Barbell Back Squat

Abstract

PURPOSE: To determine inter-set reliability of a new linear position transducer (LT) at four intensities of a one repetition maximum (1RM) barbell back squat. METHODS: Eight individuals (25 ± 5 yrs, 79.6 ± 11.6 kg, 171.1 ± 5.0 cm) with at least six months of previous resistance training and an ability to safely perform the barbell back squat reported to the laboratory twice. On visit one, participants gave written informed consent and performed a 1RM for back squat. At least 48 hours later, they returned to the laboratory to perform two sets of three repetitions of barbell back squats at 30, 50, 60, and 70% 1RM as explosively as possible, with repetitions separated by three minutes of rest. The LT was grounded and attached to the inside of the barbell sleeve with the retractable belt perpendicular to the ground. The LT measured position at a frequency at 100 Hz, while raw data was filtered using a 0.1s rolling average with repetition onset defined as a filtered velocity of 0.15 m•s-1. Average (AV) and peak velocity (PV), as well as barbell displacement (D) were calculated from the best repetition (BR), defined as the repetition with the highest AV, and the average of three repetitions (AR) for all intensities. Reliability was determined via two-tailed dependent samples t-test and Intraclass Correlations. RESULTS: Data are presented in Table 1. Strong reliability was displayed for AR in AV, PV, and D, as well as BR in AV and PV at all intensities. Moderate reliability was noted for BR in D at 30, 50, and 60% 1RM with a strong reliability at 70% 1RM. There were no differences between any variable at any intensities in AR or BR CONCLUSIONS: Data indicate strong inter-set reliability of the new LT based on AR for AV, PV, D and BR for AV and PV at varying back squat intensities. Given the range of individual training history, practitioners should interpret BR D with caution, as reliability was reduced, especially at 60% 1RM. Future research should compare LT reliability among different training statuses.