Frequency characteristics of team sport movements: an inertial measurement unit accelerometer analysis

This study analysed the frequency domain characteristics of acceleration data from upper-body mounted inertial measurement units across a controlled and game environment. Understanding the frequency content of such data can inform the selection of sampling frequencies for wearable athlete tracking systems. Two cohorts were used for this study (I) thirteen competitive male and female athletes who completed a circuit representative of common team sport movements with data collected using a research-grade inertial measurement unit sampling at ~ 1136 Hz; and (II) Game data of twenty-three elite male Australian Football athletes collected using a Global Navigation Satellite System-embedded inertial measurement unit sampling at 100 Hz during one full match. Two spectral metrics were derived from one-sided power density estimates: the dominant movement frequency (frequency at peak power), and the upper limit frequency at half peak power. In the controlled environment, dominant frequencies ranged from < 1.6 Hz (jump and zigzag) to 6.2 Hz for backwards running. The dominant movement frequency in the game environment was 2.8 Hz (peak power: 11 (m/s²)²/Hz), comparable to the dominant movement frequency across all controlled environment movements combined (2.8 Hz; peak power: 8.6 (m/s²)²/Hz). These findings provide preliminary evidence that the most relevant frequency content of upper-body mounted inertial measurement unit acceleration signals during team sport movements is concentrated below approximately 5 Hz. The frequency-domain reference established in this study provides a conservative estimate of the sampling requirements for monitoring whole-body athlete movement. The findings may assist practitioners and researchers in interpreting the capabilities and limitations of wearable athlete tracking systems they utilise. However, further validation across diverse sports, devices, competitive levels, and game contexts is required before firm technical guidelines can be established.