Within-Match PlayerLoad™ Patterns During a Simulated Soccer Match: Potential Implications for Unit Positioning and Fatigue Management

Purpose: To assess the acute alterations in triaxial accelerometry (PlayerLoad [PLVM]) and its individual axial planes (anteroposterior PlayerLoad [PLAP], mediolateral PlayerLoad [PLML], and vertical PlayerLoad [PLV]) during a standardized 90-min soccer match-play simulation (SAFT(90)). Secondary aims of the study were to assess the test-retest reliability and anatomical location of the devices. Methods: Semiprofessional (n = 5) and university (n = 15) soccer players completed 3 trials (1 familiarization, 2 experimental) of SAFT(90). PlayerLoad and its individual planes were measured continuously using micromechanical-electrical systems (MEMS) positioned at the scapulae (SCAP) and near the center of mass (COM). Results: There were no between-halves differences in PLVM; however, within-half increases were recorded at the COM, but only during the 1st half at the SCAP. Greater contributions to PLVM were provided by PLV, and PLML when derived from the SCAP and COM, respectively. PLVM (COM 1451 +/- 168, SCAP 1029 +/- 113), PLAP (COM 503 +/- 99, SCAP 345 +/- 61), PLML (COM 712 +/- 124, SCAP 348 +/- 61), and PLV (COM 797 +/- 184, SCAP 688 +/- 124) were significantly greater at the COM than at the SCAP. Moderate and high test retest reliability was observed for PlayerLoad and its individual planes at both locations (ICC.80-.99). Conclusions: PlayerLoad and its individual planes are reliable measures during SAFT(90) and detected within-match changes in movement strategy when the unit was placed at the COM, which may have implications for fatigue management. Inferring alterations in lower-limb movement strategies from MEMS units positioned at the SCAP should be undertaken with caution.