## 4 Discussion
Future research is needed to clearly elucidate the nuanced actions of this diverse position. The number of high-velocity efforts differ from the sprint counts observed by [PERSON] et al. [3] during collegiate football matches. Fewer high-velocity efforts were observed for WR, CB, and S than [PERSON], while linemen had more high-velocity efforts in this study. These disagreements may be explained by differences in the thresholds set to define a high velocity or sprint effort. [PERSON] used an absolute cutoff of 23 kmh\({}^{-1}\) as a sprint effort, which may over-classify sprint efforts for the faster players and under-classify sprint efforts for slower players [26]. Defining sprints based on an absolute threshold does not account for the sprint ability of slower positions, likely underestimating their high-velocity running during a game [26]. Similarly, it may overestimate the high velocity running by faster players. This study used a threshold of 85% of positional maximum velocity, which may offer a more robust representation of high-velocity activity by accounting for differences in maximum velocities and sprint capacity between positions. Such an approach could be extended in future research to create thresholds for individual athletes based on their in-game maximum velocity. One limitation of this study is that it does not examine player demands for running or other velocity zones; future studies should look at in-game loads at other thresholds. Additionally, further research should work to express the velocity demands during specific play types (run versus pass) or other discrete actions (e.g., different wide receiver routes). Due to the start and stop nature of the sport and the small spaces within which players must navigate, acceleration and deceleration become a vital component of the game. Using a threshold of 3.5 ms\({}^{-2}\), WR performed the most acceleration efforts, followed by TE on offense. On defense, S had the highest number of acceleration efforts, with LB closely following. These observations may be specific to the unique demands of tight ends and linebackers, who compete against each other. These two groups represent a hybrid or transitional type of player who is larger and not as fast as the wide receivers and defensive backs but smaller and faster than the linemen [18; 27]. As such, they perform a substantial amount of activity in small spaces, often hitting and colliding with other players, where the ability to accelerate is required. The acceleration and deceleration findings within this study were similar to observations made at the collegiate level [3], where the wide receiver and defensive backs exhibited more maximum intensity acceleration and deceleration efforts than other positions. However, the number of efforts observed for NFL athletes was greater across all positions than that seen in [PERSON]'s data despite a similar threshold being used. Athletic ability across a college team is more heterogenous than the NFL, as many of the collegiate players will not make it to the highest level of play. The NFL data may also be more reflective of the upper limits of physical performance for individuals playing the sport. More specific analysis is required to differentiate acceleration and deceleration activities during run and pass plays where positions may perform differently due to the structure of the play and the starting position of the players in the play (e.g., three-point stance versus standing up right). The physical requirements within American football diverge based on the role of each position. Importantly, defensive players should have similar physical abilities to the offensive players they cover. [PERSON] [28] found that positions who compete against each other possessed complementary physical outputs during the NFL combine, suggesting potential similarities in game demands. For example, the WR runs routes at high velocities to create opportunities to receive a pass while defensive backs try to mirror them to defend or intercept the pass.