Validity Of Linear Position Transducer To Measure Velocity During Barbell Back Squats

PURPOSE:Examine the validity of a linear position transducer (LPT) measuring velocity and displacement (D) relative to a validated criterion (CTRN) during the barbell back squat (BS). METHODS:Eight men and women (25 ± 5 years, 171 ± 5 cm, 79.6 ± 11.6 kg) with six months of prior resistance training experience completed two trials at least 48 hours apart. During visit one participants completed an informed consent and one-repetition maximum (1RM) for the BS. During visit two participants performed two sets of three BS repetitions at 30, 50, 60, and 70% 1RM. LPT and CTRN were attached to the inside sleeves of the barbell with the retractable belts perpendicular to the floor. Barbell position collected by LPT was sampled at a rate of 100 Hz and filtered on a rolling 0.10s average with a custom spreadsheet calculating peak velocity (PV), mean velocity (MV), and D. Repetition onset was defined as a filtered velocity of 0.15 m•s-1. CTRN data employed a 30 cm movement threshold and assessed for PV, MV and D. Intraclass Correlation Coefficients (ICC) and paired samples t-tests were used to assess validity and differences between both unfiltered and filtered data for LPT relative to CTRN. RESULTS:Data is displayed in Table 1. Strong ICCs were observed for PV and MV between LPT and CTRN, with filtered data reflecting higher ICCs at all intensities. Differences were noted between the LPT and CTRN for both PV and MCV whether LPT data were filtered or unfiltered at all intensities, except for PV at 30% using unfiltered data (p > 0.05). Moderate to strong ICCs were observed for D between devices, though when measured with CTRN, D was about 6 cm greater than observed with LPT (p < 0.05). CONCLUSION:Data indicate LPT provides valid measures of PV, MCV, and D, though there is likely consistent error between the LPT and CTRN. Filtered data typically display higher ICC compared to unfiltered data. Differences in D are likely due to the onset velocity for LPT, which may have caused differences between devices for PV and MV.