Accelerometry for Gym-Based Training: Comparing Resistance Versus Plyometric Training

This study used inertial measurement units (IMUs) to describe the accelerometry profiles of plyometric and resistance training, compare between sensor placements and gym session types, and evaluate the between-session reliability of accelerometry-derived metrics during plyometric training. Ten high-performance youth tennis players completed two identical plyometric sessions and one resistance session while wearing IMUs at four anatomical locations (thoracic spine, lumbar spine, left ankle, right ankle). Metrics included peak upward acceleration (PUpAcc), 1D upward PlayerLoad™ (1DPL-up), 2D PlayerLoad™ (2DPL), and 3D PlayerLoad™ (3DPL). All metrics were significantly higher at the ankles than the thoracic or lumbar sites (p < 0.05), consistent with signal attenuation across the kinetic chain. For vertical loading in isolation, 1DPL-up demonstrated stronger thoracic-ankle relationships (r = 0.47–0.70) although only one of four correlations was statistically significant, compared with PUpAcc (r = −0.67–0.27; all p > 0.05). At the thoracic site, between-session reliability during plyometric training was poor for 1DPL-up (ICC = 0.49) and moderate for PUpAcc (ICC = 0.53). All thoracic-derived metrics differentiated plyometric from resistance sessions (p < 0.05). These findings indicate that thoracic-mounted IMUs provide moderately reliable, session-sensitive information on peak vertical accelerometry loads in gym-based training. However, the limited inter-sensor agreement for PUpAcc highlights the need for further refinement to enhance practical utility. Overall, accelerometry appears feasible for integrating gym-based training loads into holistic daily training load monitoring.