# Relationship between ground reaction force and sacrum acceleration during 180° change of direction maneuvers in elite female basketball players

## TL;DR

This study explores how sacrum acceleration relates to ground reaction force during directional changes in elite female basketball players.

## Contribution

The study introduces ACCIMU as a potential real-world method to estimate GRF during specific basketball maneuvers.

## Key findings

- Peak horizontal ACCIMU was significantly higher than GRFrel across all conditions.
- ACCIMU correlated with GRFrel during lateral shuffle but not during 180° turn maneuvers.
- Peak resultant ACCIMU showed significant correlation with peak horizontal GRFrel.

## Abstract

This study investigated the relationship between sacrum acceleration (ACCIMU) 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.

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 (GRFrel), whereas peak horizontal and resultant ACCIMU were expressed relative to gravitational acceleration, allowing direct comparison between dimensionless quantities.

Reliability across the two trials was assessed using intraclass correlation coefficients (ICC2,2) and coefficients of variation (CV), and was acceptable for most variables (ICC2,2 = 0.67–0.95; CV% = 3.85–12.74%). Paired t-tests revealed that peak horizontal ACCIMU was significantly greater than peak horizontal GRFrel 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 ACCIMU and peak horizontal GRFrel during the lateral shuffle (r = 0.55–0.69, p < 0.05), with the ACCIMU increasing proportionally to the GRFrel (slope = 4.55–5.23), but not during the 180° turn (r = 0.33–0.49, p > 0.05). Peak resultant ACCIMU was significantly correlated with peak horizontal GRFrel (r = 0.64–0.72, p < 0.05) and exhibited proportional bias (slope = 2.61–4.70).

These results indicate that, despite potential software-related errors and estimation uncertainties, ACCIMU monitoring represents a promising method for estimating peak horizontal GRFrel demands during task-specific 180° COD maneuvers in real-world settings.