Concurrent Validity and Between-Session Reproducibility of Agreement of GPath for Mean Propulsive Velocity Assessment...

Growing use of inertial measurement units (IMUs) in velocity-based training has outpaced the evidence supporting their accuracy, making device-specific validation an essential aspect before adoption in research or practice. This study evaluated the concurrent validity of the GPath 6-axis inertial sensor against the Chronojump linear position transducer (LPT) for mean propulsive velocity (MPV) measurement during the bench press exercise. Twelve physically active males performed repetitions at 20%, 40%, 60%, and 80% of one-repetition maximum (1RM) across two separate testing sessions. Concurrent validity was evaluated using Pearson's correlation, concordance correlation coefficient (CCC), Bland-Altman analysis, typical error, and coefficient of variation (CV). The GPath systematically overestimated MPV relative to the LPT at all loading conditions (p < 0.001), with bias decreasing from 0.253 m/s (20% 1RM) to 0.091 m/s (80% 1RM). CV remained low and consistent across conditions (5.12-5.98%). CCC was trivial > 1 m/s (20-40% 1RM: 0.079-0.056; combined: 0.331) and moderate < 1 m/s (60-80% 1RM: 0.430-0.433; combined: 0.833), with an overall CCC of 0.877. Between-session reproducibility of agreement was high (Session 1: CCC = 0.878; Session 2: CCC = 0.877), with between-session bias differences not exceeding 0.026 m/s. Despite its systematic overestimation, the GPath showed a reproducible bias structure between sessions, which may indicate utility for longitudinal within-athlete monitoring of relative MPV changes. Although, it cannot be recommended for absolute velocity measurement or 1RM estimation without prior correction.