Validity, Reliability, and Sensitivity of a Commercially Available Velocity Measuring Device When Performing Selected Exercises.

The aim of this study was to determine the validity, reliability, and sensitivity of a new linear position transducer (LPT) device (RepOne) to a previously validated LPT (Tendo) during the barbell back squat and bench press exercises. Fourteen recreationally resistancetrained individuals (7 males and 7 females) performed three repetitions for the back squat and bench press at loads ranging from 30-90% 1RM. Both devices recorded average (ACV) and peak (PCV) concentric velocities concurrently for every repetition at each load. Significant correlations were observed between RepOne and Tendo during the back squat (PCV: = 0.90-0.99, < 0.01; ACV: = 0.84-0.99, < 0.01), bench press (PCV: = 0.74-0.99, < 0.01; ACV = 0.81-0.99, < 0.01). ICCs reveal good to excellent reliability between devices for back squat (PCV, 0.85-0.99; ACV, 0.83-0.99) and bench press (PCV, 0.79-0.99; ACV, 0.83-0.99). Bland-Altman plots revealed greater bias during PCV for both exercises across intensities (back squat, 0.072 to 0.110 m/s; bench press, 0.039 to 0.107 m/s), although ACV bias was lower for both exercises (back squat, -0.002 to -0.029 m/s; bench press, -0.022 to 0.015 m/s). The RepOne device generally exhibited higher smallest detectable change (SDC) values compared to the Tendo, except for specific loads in certain conditions. Additionally, the RepOne device demonstrated higher smallest worthwhile change (SWC) values than the Tendo unit for most loads in back squat ACV. Collectively, the RepOne exhibits strong validity and reliability comparable to the Tendo across both barbell back squat and bench press exercises, despite some variations in sensitivity metrics like SDC and SWC, indicating its efficacy for resistance training application.