A Comparison of Tri-Axial Accelerometer Derived Pre-Season, In-Season, and Game Demands in NCAA Division I Football Players

Abstract

PURPOSE: A tri-axial accelerometer, combined with a magnetometer and gyroscope, can quantify directional movement in three planes of motion. This type of device is often used to measure external workloads (i.e. PlayerLoadTM [PL]) and workload intensity (i.e. PL per minute [PLPM]), during training in collegiate football athletes. This study investigated the percentage of external load contribution by axis (i.e. mediolateral, anteroposterior, and vertical) between seven football positions during summer training, in-season training and games, and within positions between summer training, in-season training and games. METHODS: PlayerLoadTM was measured among 59 NCAA Division I football athletes using Catapult Optimeye S5 (13 Defensive Backs [DB], 9 Wide Receivers [WR], 5 Running Backs [RB], 4 Tight Ends [TE], 12 Linebackers [LB], 11 Defensive Linemen [DL], and 6 Offensive Linemen [OL]). PlayerLoadTM per minute was derived by dividing PL by duration. PlayerLoadTM percentages were determined by dividing PL by each PL axis (anteroposterior [PLAP], mediolateral [PLML], and vertical [PLV]). Linear mixed effects models with random intercepts for player and date were used to assess position specific differences – with respect to percent PL distribution – in the three dimensions. Pairwise differences between positions were not adjusted for multiple comparisons. A linear mixed effect model with random intercepts for player and data was used to assess intra-positional differences from summer training to in-season training. RESULTS: Position had an effect on PL, PLPM, and PL distribution during summer training, in-season training and games. Season had a significant effect on percent load distribution within position. The PLAP for all positions, except TE, LB and OL, was significantly higher during summer training, compared to games (p < 0.001). The PLML for all positions was significantly lower during summer training, compared to games (p < 0.001). The PLV for all positions, except DL, was significantly higher during summer training (p < 0.01). PlayerLoadTM was significantly higher for all positions during in-season training compared to summer training, however, PLPM was significantly lower for all positions. CONCLUSION: Both intra-positional, between summer training, in-season training and games, and inter-positional PL, PL¬PM, and PL distribution differences, by season, were observed. The inter-positional differences are relatively small in absolute terms and may not be meaningful from a positional standpoint. The intra-positional differences suggest that the training done during the summer sessions does not reflect expected in-season training session and game demands. This is especially true of the PLML axis with summer values ranging 4.02-6.9% lower than game values. The off-season is typically utilized to prepare athletes for the rigor of the in-season. Future studies should examine the demands of the game to select appropriate training loads.