Background: Investigations into hamstring strain injuries at the elite level exist in sports such as Australian Rules football, rugby, and soccer, but no large-scale study exists on the incidence and circumstances surrounding these injuries in the National Football League (NFL).
Hypothesis: Injury rates will vary between different player positions, times in the season, and across different playing situations.
Study Design: Descriptive epidemiology study.
Methods: Between 1989 and 1998, injury data were prospectively collected by athletic trainers for every NFL team and recorded in the NFL’s Injury Surveillance System. Data collected included team, date of injury, activity the player was engaged in at the time of injury, injury severity, position played, mechanism of injury, and history of previous injury. Injury rates were reported in injuries per athlete-exposure (A-E). An athlete-exposure was defined as 1 athlete participating in either 1 practice or 1 game.
Results: Over the 10-year study period 1716 hamstring strains were reported for an injury rate (IR) of 0.77 per 1000 A-E. More than half (51.3%) of hamstring strains occurred during the 7-week preseason. The preseason practice IR was significantly elevated compared with the regular-season practice IR (0.82/1000 A-E and 0.18/1000 A-E, respectively). The most commonly injured positions were the defensive secondary, accounting for 23.1% of the injuries; the wide receivers, accounting for 20.8%; and special teams, constituting 13.0% of the injuries in the study.
Conclusion: Hamstring strains are a considerable cause of disability in football, with the majority of injuries occurring during the short preseason. In particular, the speed position players, such as the wide receivers and defensive secondary, as well as players on the special teams units, are at elevated risk for injury. These positions and situations with a higher risk of injury provide foci for preventative interventions.
Background: Hamstring strains remain one of the most prevalent injuries in Australian Rules football. The authors prospectively examined the relationship between musculotendinous stiffness of the hamstring and leg stiffness with hamstring injury in professional Australian Rules footballers during the 2006 season.
Hypothesis: Higher hamstring stiffness and leg stiffness are related to noncontact, soft tissue hamstring injury risk in professional Australian Rules footballers.
Study Design: Case-control study; Level of evidence, 3.
Methods: Unilateral hamstring stiffness and leg stiffness were assessed in 136 professional footballers in the month before the commencement of the competitive season. This information was then investigated relative to players who suffered noncontact, soft tissue hamstring injuries during either matches or training throughout the season to identify whether preseason stiffness was related to injury occurrence.
Results: Fourteen tested players recorded acute, noncontact hamstring injuries, resulting in 3.3 ± 2.8 weeks of missed match play per injury. At preseason testing, the players who ended up sustaining a hamstring injury during the season recorded significantly higher mean hamstring stiffness (11%, P = .04) and leg stiffness (5%, P = .03). When considering the injured players, the leg stiffness of the involved limb was significantly higher than the noninjured players (P = .02), whereas hamstring stiffness was significantly higher on the noninvolved limb (P = .01). Further, those players who suffered a hamstring injury were significantly older than the noninjured players (P = .01).
Conclusion: It appears that a high bilateral hamstring stiffness and leg stiffness may be a determinant in the risk of sustaining a hamstring injury. Further, relatively lower hamstring stiffness in the involved limb of injured players appears to be associated with increased injury and may be related to a lack of strength. The information from stiffness assessment may allow medical staff to determine the hamstring risk status for individual players in team sports.
