Reliability and Accuracy of Linear Position Transducers During the Bench Press and Back Squat: Implications for Velocity-Based Training

<b>Background:</b> Selecting the right linear position transducer (LPT) for velocity-based training monitoring sometimes presents uncertainties for coaches. <b>Objectives:</b> This study rigorously examined the test-retest reliability of three LPT-Cs using a simultaneous triangulation method of the same device during bench press (BP) and back squat (SQ) exercises performed on a Smith machine. <b>Methods:</b> Forty university students-13 females (23 ± 2 years) and 27 males (31.5 ± 6 years)-voluntarily participated in a randomized repeated-measures study. LPTs were randomly assigned numbers and placed at 5 cm apart to measure and collect bar displacement (∆S), mean propulsive velocity (MPV), peak velocity (PV), and time to peak velocity (T-PV). Each volunteer performed three BP and SQ attempts with pre-standardized loads (males: BP ≥ 40 kg and SQ ≥ 60 kg; females: BP ≥ 25 kg and SQ ≥ 40 kg). <b>Results:</b> The main findings of this study support a high degree of reliability for LPTs. For all variables, the absolute reliability presented significant values (<i>p</i> ≤ 0.05), with an intraclass correlation coefficient ≥ 0.995, a 95% confidence interval between 0.992-0.999, a coefficient of variation ≤ 10%, and a standard error of the mean ≤ 0.031. <b>Conclusions:</b> Scientists and coaches can use the LPT device as a reliable tool for monitoring velocity-based training by providing rigorous measurements of ∆S, MPV, PV, and T-PV during BP and SQ exercises. In addition, the smallest real difference reported may be useful in identifying minimal changes in ∆S within a single set (BP = 0.10 cm; SQ = 0.13 cm).