Elliott et al. examined hamstring strains among NFL football players in 2011 [9]. They retrospectively reviewed prospectively collected data from 1989 to 1998. Over 10 years, 1,716 hamstring strains occurred, an incidence of 0.77 injuries per 1,000 athletic exposures. Per year, this averaged out to 144 players sustaining 172 hamstring strain injuries. The rate of injury was noted to be much higher during preseason practices as opposed to in-season practice sessions; 47.3 % of all injuries occurred during games, though. Positions that are reliant on explosive speed, such as defensive backs and wide receivers, accounted for 43.9 % of all strains. Special teams players, notably punters, had a high incidence as well. This paper’s findings determined that the average player missed 13.2 days due to a single hamstring strain (median 9 days per injury).

Complete hamstring rupture is an uncommon event in the NFL [10]. This injury was reported via the NFL Injury Surveillance System ten times in the time period between 1990 and 2008. Mean age at the time of injury was 27.2 years old. All injuries occurred in the regular season, and 8/10 occurred after week 4. The breakdown by position was two defensive backs, two defensive linemen, two linebackers, one quarterback, one wide receiver, one running back, and one tight end. Six of ten players recalled hip hyper-flexion coupled with knee extension. Other injured athletes recalled running and cutting. Three players recalled prodromal symptoms. This particular study attempted to determine how successful athletes were at returning to play after this event. Nine out of ten returned to play. The one player who did not return to play showed symmetric strength between legs, but subjectively reported diminished speed. Four players returned to play, but only played in one game. Interestingly, one player had a complete proximal hamstring rupture of the contralateral side shortly thereafter. Neither of the two undrafted players who had this injury returned to play more than one game.

In collegiate football, the most comprehensive study is from the Journal of Athletic Training in 2007 [11]. This paper reported on 16 years of epidemiologic data reported via the Injury Surveillance System. They stated that during the 16-year reporting period, 19 % of NCAA institutions sponsoring football participated in the Injury Surveillance System. There was little variation in overall injury rate over time. Regarding all injuries (not just hamstring strains), they noted 36 injuries per 1,000 athlete exposures (A-Es) during games. In fall practice, they noted approximately four injuries per 1,000 A-Es. In spring practice, they noted about ten injuries per 1,000 A-Es. When looking specifically at hamstring strains, data from this study was grouped as “muscle-tendon strain” of the upper leg, thus this could include quadriceps and hamstring strains both. Regardless, they reported data in three separate groups, which were fall games, fall practices, and spring practice. In the 16 years during fall games, there were 1,103 upper leg strains. This accounted for 3.6 % of all injuries. During games, the injury rate per 1,000 athlete exposures was 1.24. Fall practices showed 4,518 thigh strains, accounting for 10.7 % of practice injuries. The injury rate per 1,000 athlete exposures was found to be 0.41. And in spring there were far less upper leg strains, 1,179. Similar to fall practices, the percentage of injuries from this condition was 10.8 %. And the injury rate per 1,000 athlete exposures in the spring was 1.04.

Hamstring injuries in professional rugby players have received a particularly significant amount of attention in the past. This is due to the common nature of this injury in this particular population of athletes. In a paper out of the UK published on the Rugby Football Union they noted 16,782 h of match exposure and 196,409 h of training exposure which resulted in 164 hamstring strains (0.27 injuries/1,000 player hours) [12]. The incidence of injury in matches was 5.6 injuries per 1,000 player hours. In total this caused 2,707 days of absence from training or competition. Injuries were graded as minor, moderate, or major based on time missed from participating (≤1, 1–3, and ≥3 weeks, respectively). They found that 37 % were minor in nature, 37 % moderate, and 26 % were called severe. They noted that the incidence of hamstring injuries seemed to increase as matches reached the last quarter (minutes 61–80) of competition. Interestingly, substitute players showed a higher rate of injury at a level of 10.7 injuries per 1,000 h. The highest incidence of strains occurred during running activities, but more severe injuries were a result of kicking activities (average 36 days lost to training or matches). They evaluated demographics of participants and did not note any significant differences in the incidence of hamstring injuries as a function of age, height, body mass, or BMI. The incidence of injury among backs was four times higher in players of African or Caribbean descent as opposed to Caucasians.

Football injuries in Australia have been surveyed extensively as well. Verrall et al. suggested that 30 % of Australian football players in two clubs had posterior thigh pain over one season [13]. Orchard and Seward have long-term data on this unique epidemiology [14–16]. Amongst three leagues in the 1992 season, they reported 2,398 injuries in 57 teams. Hamstring strains were the most commonly reported injury in Australian Rules football (13 %) of all injuries recorded. Head and face lacerations were more common in rugby players (Rugby League and Rugby Union). Injuries tended to occur in the middle segments of matches, and more injuries happened at the beginning of the season compared to later months of the season. Of all hamstring strains, 34 % were recurrent injuries. Hamstring strains accounted for the most time missed from participation. In the discussion section of this particular paper they compared injuries in the Australian Football League (AFL) to a prior paper that described injury trends in the Victorian Football League during the 1983–1985 seasons. They noted that hamstrings strains have been increasing in incidence (8.9 % of injuries in past to 13.4 % in the 1992 season). Orchard and Seward again evaluated epidemiologic data in the AFL, this time from 1997 to 2000. This subsequent data again showed hamstring strains as the most common affliction of all injuries. About six hamstring strains occurred per season per club of 40 players. This represented 15 % of all injuries. Hamstring strains again showed the highest rate of recurrence of all injuries. There were approximately 3.7–4.3 strains per 1,000 player hours in matches. Most recently the group published their data again in the American Journal of Sports Medicine in April of 2013 (Table 3.2). They looked at their data from the AFL from 1992 to 2012. There were a total of 2,253 new hamstring injuries and 588 recurrent injuries, causing 7,322 matches to be missed. The average recurrence rate was 26 %. Each club missed an average of 20.4 matches per player per club season due to hamstring strain. They noted over the 21 years that players took longer to return to play after muscle injuries, and recurrence rates tended to decrease as time went on. However, severity of injury with regard to amount of matches missed tended to slightly increase over time.