Reliability of the HUMAC360 to Measure Movement Velocity during Three Equal Segments of the Barbell Back Squat

Introduction: Linear position transducers (LPT) are commonly used to assess movement velocity during full concentric movements, but fail to account for fluctuations in velocity throughout the movement. This investigation aimed to determine inter-set and inter-day reliability of the HUMAC360 LPT during three equal segments of the barbell back squat. Methods: Seventeen participants with resistance exercise experience completed an informed consent and a one-repetition maximum (1RM) on their initial visit, with two additional visits consisting of two sets of three repetitions at 30-, 50-, 60- and 70% of 1RM with ≥ 48H between visits. The LPT was attached to the medial aspect of the barbell sleeve to assess velocity. Repetitions were segmented into thirds based on distance as the top, middle and bottom portion of the movement. Intraclass Correlation Coefficients (ICC), standard error of the measurement and paired samples t-tests were used to assess mean velocity (MV), peak velocity (PV) and duration reliability. Results: When using the average of the three repetitions, good-to-excellent (ICC2,1=0.708-0.993) inter-set and inter-day MV and PV ICCs were noted across all intensities and segments. The top and middle portion exhibited stronger reliability measures compared to the bottom. Movement velocity was not significantly different (p>0.05) at any exercise intensity, with the exception of MV at 60% during the top portion of the movement (p=0.045). Conclusions: The HUMAC360 provides reliable measures of mean velocity and peak velocity during each segment of the barbel back squat.