Validity and between-unit agreement of commercially-available linear position transducer and inertial sensor devices during loaded countermovement jumps.

To assess the validity and between-unit agreement of velocity monitoring devices during incrementally-loaded countermovement jumps (CMJ), 16 males (24.0 ± 3.5 yr) completed 12 CMJs on a force plate (FP). Performance variables were collected through two linear position transducers (GymAware [GA]) and four accelerometer-based devices (two PUSH units, two Bar Sensei units). Pearson correlations (<italic>r</italic>) and coefficients of variation (CV) demonstrated <italic>strong</italic> to <italic>very-strong</italic> relationships (<italic>r</italic> = 0.60–0.88) and <italic>poor</italic> agreement (CV = 11.7–25.3%) between FP and GA, and <italic>moderate</italic> to <italic>very-strong</italic> relationships (<italic>r</italic> = 0.31–0.81) and <italic>poor</italic> agreement (CV = 10.1–24.2%) between FP and PUSH. Between-unit comparisons demonstrated <italic>moderate</italic> to <italic>very-strong</italic> relationships (<italic>r</italic> = 0.50–0.88) with <italic>poor</italic> agreement (CV = 10.8–26.6%) for GA, and <italic>very weak</italic> to <italic>very-strong</italic> relationships (<italic>r</italic> = 0.01–0.87) with <italic>moderate</italic> to <italic>poor</italic> agreement (CV = 9.1–24.1%) for PUSH. Bar Sensei units were excluded from analyses. Loaded CMJ data collected with either device displayed <italic>poor</italic> agreement with a FP. Velocity monitoring devices demonstrate poor validity across all loads; however, GA demonstrated strong between-unit agreement. A FP should be utilised to accurately assess CMJ performance at all times. [ABSTRACT FROM AUTHOR]