PlayerLoad™: Reliability, Convergent Validity, and Influence of Unit Position During Treadmill Running

Barrett S., Midgley A., Lovell R.

Purpose: This study aimed to establish the test-retest reliability and convergent validity of PlayerLoadTM (triaxial-accelerometer data) during a standardized bout of treadmill running.

Methods: Forty-four team-sport players participated in 2 standardized incremental treadmill running tests (7-16 km/h) 7 days apart. Players’ oxygen uptake (V02; n = 20), heart rate (n = 44), and triaxial-accelerometer data (PlayerLoad; n = 44) measured at both the scapulae and at the center of mass (COM) were recorded. Accelerometer data from the individual component planes of PlayerLoad (anteroposterior [PLap], mediolateral [PLMl], and vertical [PLv]) were also examined.

Results: Moderate to high test-retest reliability was observed for PlayerLoad and its individual planes (ICC > 0.80-0.97, CV 4.2-14.8%) at both unit locations. PlayerLoad was significantly higher at COM vs scapulae (223.4 ± 42.6 vs 185.5 ± 26.3 arbitrary units; P = .001). The percentage contributions of individual planes to PlayerLoad were higher for PLMl at the COM (scapulae 20.4% ± 3.8%, COM 26.5% ± 4.9%; P = .001) but lower for PLv (scapulae 55.7% ± 5.3%, COM 49.5% ± 6.9%; P = .001). Between-subjects correlations between PlayerLoad and V02, and between PlayerLoad and heart rate were trivial to moderate (r = -0.43 to 0.33), whereas within-subject correlations were nearly perfect (r = 0.92-0.98).

Conclusions: PlayerLoad demonstrated a moderate to high degree of test-retest reliability and showed convergent validity with measures of exercise intensity on an individual basis. However, caution should be applied in making between-athlete comparisons.