Background This study investigated the relationship between sacrum acceleration (ACC IMU ) measured using an inertial measurement unit (IMU) and ground reaction force (GRF) measured using force plates during 180° change of direction (COD) maneuvers in elite female basketball players. Methods Fourteen Japanese national female basketball players performed two types of 180° COD tasks (lateral shuffle and 180° turn maneuvers) on force plates while wearing a sacrum-mounted IMU, completing two trials in each direction (left and right). The peak horizontal GRF during plant foot contact was normalized to body weight (GRF rel ), whereas peak horizontal and resultant ACC IMU were expressed relative to gravitational acceleration, allowing direct comparison between dimensionless quantities. Results Reliability across the two trials was assessed using intraclass correlation coefficients (ICC 2,2 ) and coefficients of variation (CV), and was acceptable for most variables (ICC 2,2 = 0.67–0.95; CV% = 3.85–12.74%). Paired t -tests revealed that peak horizontal ACC IMU was significantly greater than peak horizontal GRF rel across all conditions ( p 0.001, d = 0.56–1.06). Pearson correlation and ordinary least products regression analyses demonstrated a significant association between peak horizontal ACC IMU and peak horizontal GRF rel during the lateral shuffle ( r = 0.55–0.69, p 0.05), with the ACC IMU increasing proportionally to the GRF rel (slope = 4.55–5.23), but not during the 180° turn ( r = 0.33–0.49, p 0.05). Peak resultant ACC IMU was significantly correlated with peak horizontal GRF rel ( r = 0.64–0.72, p 0.05) and exhibited proportional bias (slope = 2.61–4.70). Conclusion These results indicate that, despite potential software-related errors and estimation uncertainties, ACC IMU monitoring represents a promising method for estimating peak horizontal GRF rel demands during task-specific 180° COD maneuvers in real-world settings.
Ogata et al. (Wed,) studied this question.