The Influence of the Inertial Motor Unit Location (Lumbosacral vs. Thoracic Regions) on the External Load Registered During Badminton Matches

The use of inertial motor units (IMUs) to monitor external training loads during training and competition has grown, particularly in racket sports like badminton. Previous studies highlighted the influence of sensor location on external load measurements, with the lumbosacral region identified as optimal. However, IMUs are often placed dorsally between the scapulae. This study examined the impact of IMU placement (lumbosacral vs. thoracic) on external load recordings during two simulated badminton matches. Sixteen junior international-level players (10 males, 6 females) participated in matches designed to replicate worst-case scenarios (2 × 35 min, 15 min rest). IMUs located on the lumbosacral joint (L) and thoracic area (T) recorded data combining Ultra-Wideband and acceleration technologies. The results showed higher total and sprint distances in T than L (1.0-3.6%, pη² = 0.089-0.182). Small differences were noted for accelerations and decelerations (1.5%, pη² = 0.057) with no significant differences in speed. Conversely, L showed higher values for total impacts and player load (34.6-49.8%, pη² = 0.861-0.868). The findings reveal slight discrepancies in distance and speed based on placement but significant differences in impacts and player loads, warranting further investigation.