Risk Factors for Injuries in College Football: A Systematic Review

Introduction

Foremost, colleges and universities are a place for student intellectual development. Even students who play for NCAA teams are called “student-athletes.” Most students in the United States enter college at the age of 18 years. Learning during college years occurs in various forms (i.e., academic, sports, and emotional experiences; Krill et al., 2020; Meyer et al., 1994). Students who participate in college sports are prone to injuries that can be minor or major (Kmush et al., 2020). Major injuries can sometimes have a long-term impact on the physical capabilities of these students and can also disrupt the goals of professional play. As the highest level of collegiate play in the United States, National Collegiate Athletic Association (NCAA) Division I athletics programs attract most of the strongest, fastest, and most skilled collegiate athletes of any given sport. Overwhelmingly, college football is the top NCAA sport in terms of revenue and number of athletes participating (Krill et al., 2020; Meyer et al., 1994). It also features the highest historical injury rate (IR) among NCAA sports for both practices and games (Hootman et al., 2007). The types of injuries observed in college football include brain injuries, spine injuries, shoulder injuries, pectoralis ruptures, acromioclavicular joint injuries, and brachial plexus injuries with the potential to cause long-term health consequences (Dick et al., 2007; National Collegiate Athletic Association, 2018).

In recent years, sports epidemiological research has focused on understanding primary risk factors associated with injuries in college football (Boden et al., 2013; Burke et al., 2020). The NCAA reports that only 1.6% of NCAA football players go on to an NFL career most NCAA football players; therefore, collegiate play does not represent an apprentice experience but rather provides an opportunity to further their education while extending their football career to the highest amateur level (National Collegiate Athletic Association, 2024). For these players, it is important to consider these functions alongside the injury toll and long-term health impacts of the sport. Even for players who will advance to National Football League (NFL) play, it is important to consider the extent of injuries in the NCAA as an impediment to the apprenticeship mechanism of NCAA play. Learning and improving as a football player from the sidelines is difficult. This research intends to grow public understanding of risk exposures associated with high-level play and to inform rule changes needed to make the sport safer for participants. In this article, we systematically reviewed previous research on the topic of risk factors for injury in college football. We evaluated all scientific research articles published on various platforms that meet our inclusion and exclusion criteria.

Methods

We conducted systematic searches of the existing literature to gather valid information on risk factors associated with injuries among NCAA Football players. Specifically, we searched three electronic databases: PubMed, PsycINFO, and Web of Science for articles published from January 1, 1970 to December 31, 2021. We also searched previous systematic reviews and selected study bibliographies for additional articles. The search strategy included the use of combinations of the following keywords: (1) population of interest (NCAA Football players): NCAA, NCAA Football, and College Football; (2) outcome of interest (mortality): injury, sprain, and concussion; and (3) risk factors: exposures, risk, risk factors, mediators, and moderators. The search results were limited to English-language text.

Study Eligibility, Selection, and Qualitative Assessment

Our search strategy was in in three phases. In phase 1, we screened all documents retrieved based on title and abstract. Two exclusion criteria in Phase 1 were (1) studies that were not related to American College football and (2) no original data. The full text of articles moved to phase 2 were reviewed to determine their eligibility. Eligible articles were those that examined (1) NCAA Football populations, (2) injury outcomes, and (3) risk factor measures of association. We excluded case series and reports. In phase 3, all eligible articles were moved into standardized electronic forms developed in Microsoft Excel. The data included study characteristics (design, demographics, period, and duration of the study), participant selection, and ascertainment of outcomes and exposures (risk factors). In phase 3, the authors independently evaluated articles for their epidemiological quality. The authors assessed eight signaling questions informed by the Strengthening the Reporting of Observational Studies in Epidemiology guidelines to summarize five quality domains relevant to observational studies. These include participant selection, prognostic/confounding factors, cointervention exposure, exposure assessment, and outcome assessment. We summarized each domain with a rating of low, moderate, or high risk of bias. We assigned studies with a low risk of bias across all five domains with a “good” overall quality rating. Studies with ≥1 moderate, and high-risk ratings were assigned a “fair” and “poor” overall quality rating, respectively. Disagreements or uncertainties were resolved through discussion.

Operational Definitions of Injury

In this study, the NCAA Injury Surveillance System’s definition of an injury was used to determine the injuries that were analyzed. The criteria for an injury were “(1) occurred as a result of participation in an organized intercollegiate practice or competition and (2) required medical attention by a team certified athletic trainer or physician and (3) resulted in a restriction of the student-athletes participation or performance for one or more calendar days beyond the day of injury.” This definition was taken into consideration when deciding which articles would be included.

Summary Measures of Injury Risk Factor Associations

The following injury risk measures of association were examined in the selected studies: rate ratio (RR), odds ratio (OR), Kruskal–Wallis test, IR, chi-squared and r-squared values, and correlation coefficients. We reviewed 81 relevant studies categorized based on the type of injury and associated risk factors. The injury categories include concussion or brain injury, hip injury, lower extremity injury, stinger injury, turf toe injury, depression, elbow injury, shoulder injury, cervical injury, ankle injury, knee injury, hand and wrist injury, back injury, fatality, infection or sickness, fracture, and other injuries that did not fit into any of the previously listed categories.

Risk Factors for All Injuries

The incidence rate of any type of injury during games was three(Krill et al., 2020) to nine (Dick et al. (2007) times higher than during practice with higher risk during the spring than fall seasons. Chandran et al. (2021) found that the IR during a competition (game) was 6.45 times higher than during practice, whereas Kay et al. (2017) study found that the injury risk during a competition was 8.51 times higher than during practice. Risk of injuries also differed by duration and type of athlete exposures. Kerr et al. (2016) found that the IR was 36.94 per 1,000 athlete exposures in games and scrimmage, compared to 15.7 per 1,000 athlete exposures during practice. Live contact exposures were seven times more likely to result in injuries than non-contact exposures (Krill et al., 2017). Athletes exposed to average inertial load or frequent game conditions had an OR of 8.04 for injury (Wilkerson, 2012). However, in contrast, some studies have found no significant difference in injury risk based on the type of practice (Smith & Baer, 2020; Burke et al.,2020). Sampson et al. (2018) showed that IRs were similar across different positions but risk was three-fold higher (RR of 3.05) with higher acute workloads (Sampson et al., 2019).

Risk Factors for Specific Injuries

Concussions: We identified several factors (type of football helmets, field conditions, injury site, and depression) that contribute to the risk of concussion or brain-related injuries. Zemper (1994) reported the concussion rates per 1,000 athlete exposures for different types of football helmets. The Bike Air Power had the highest rate (.54), followed by the Bike Pro Air (.30), and the Riddell M155 (.13). Kerr et al., 2015 observed a higher rate of concussion (RR of 1.99) in fully padded practices compared to practices with shells worn. The Revolution helmet had a 46.1% higher risk of sustaining a concussion than the VSR4 helmet (Rowson et al., 2014). However, the type of mouthguard used did not appear to impact the risk of concussion significantly (Wisniewski et al., 2004). Overall, games had a higher risk of concussion than practices, and hits on the top or side of the head had a greater impact than those on the front (Houck et al., 2016; Liao et al., 2016). The risk of a concussion was significantly higher for games played at higher altitudes compared to lower altitudes (Lynall et al., 2016). Moreover, the younger a football player was when they sustained their first concussion, the higher their risk was for future concussions (Caccese et al., 2020; Singh et al., 2014).

The relationship between depression, stress and concussion risk is complex, but both psychological factors and repeated head trauma have been shown to significantly impact a player's mental and physical health(Mann et al., 2016). Players who have pre-existing depression tend to have a higher risk of suffering a concussion, while those who sustain concussions, especially recurrent ones, showed an increased risk for developing depression. For instance, individuals with three or more concussions had a higher prevalence of depression compared to those with no history of concussions, with a prevalence ratio of 2.6 for mental component summary (MCS; Kerr et al., 2018; Williams et al., 2017). Both a history of concussion and head impact exposure were positively associated with depression, with beta coefficients of .48 and .49, respectively (Montenigro et al., 2017)

Hip Injuries: Risk factors for hip injuries included past injury history, underlying anatomical variations, reduced hip or trunk strength, and range of motion, with previous injury being a significant predictor of future injuries (Makovicka, Chhabra, et al., 2019; Krill et al., 2018). Factors like age, time in the season, and playing position are also noted with two to three fold higher risk during games than practice (Makovicka, Chhabra, et al., 2019).

Lower extremity injuries: Studies that looked at lower extremity injury found previous concussions, structural abnormality, balance issues, level of contact in the game, types of practice, and reaction time of the player as major risk factors. Krill et al. (2018) found that individuals who had a previous concussion had an injury rate (IR) of 9.08 compared to 2.88 for those without a concussion within 12 months (incidence rate ratio [IRR] = 3.16), for lower extremity injuries. According to Lewis et al. (2020), having a structural abnormality increases the OR by 11 times for patellar tendon and 140 times for quadricep tendon injuries. College football players who scored below 89.6% on the Star Excursion Balance Test were 3.5 times more likely to sustain an injury (Butler et al., 2013). In addition, Westermann et al. (2016) showed that implementing a targeting rule in 2012 led to an increase in lower extremity injuries with a RR of 1.15. Moreover, Smith and Baer (2020) reported that the change in practice rules from 2016 to 2017 resulted in a higher IR with an RR of 1.82.

Stinger Injuries: Stinger injuries are injuries to nerves in the neck and shoulders. The risk of stinger injuries in college football was significant, with estimates ranging from 50 to 70% among players in positions like running backs, linebackers, and defensive backs due to tackling and blocking (Bartels et al., 2019; Baugh et al., 2015; Begier et al., 2004; Bradley et al., 2008; Buckley, 1988; Cahill & Griffith, 1979; Chung et al., 2019; Dick et al., 2007; Kaplan et al., 2011; Kerr et al., 2016; Krill et al., 2016, 2017; McCunn et al., 2017; Meyers, 2010; Sampson et al., 2019).Type of hit was a major risk factor, with 36.7% of stinger injuries occurring due to tackling and 25.8% due to blocking (Green et al., 2017). Consistent with other injuries, the risk of stinger injuries was 8-12 fold higher during games compared to practices (Chandran et al., 2021; Green et al., 2017).

Turf toe injuries: Turf toe injuries occur when the foot becomes “stuck” on a surface and the toes are subsequently hyperextended. Artificial turf tends to be stickier than natural grass, leading to an increased risk for such hyperextensions. Higher risk of injury has been observed during game (vs practice) and on artificial turf (vs natural grass). Athletes were 14 times more likely to sustain a turf toe injury in games than in practice and IR on artificial playing surfaces was .087 per 1,000 athlete exposures compared to .047 per 1,000 athlete exposures on grass playing surfaces.

Elbow Injuries: Elbow injuries had an incidence rate of approximately 1.85 to 1.94 per 10,000 athlete exposures due to overuse conditions like tendinitis and ligament strains to more acute issues like fractures and dislocations (Hassebrock et al., 2019; Christopher et al., 2019). Poor throwing mechanics, structural issues, fatigue, and improper training loads especially for quarterbacks during games (vs practice) plays were significant risk factors (Christopher et al., 2019).

Shoulder Injuries: Shoulder injuries account for 10% to 20% of all injuries among NCAA football players (Krill et al., 2020; Kerr et al., 2016; Sampson et al., 2019), with labral tears and dislocations being common. Overall risk of shoulder injuries was 8 (Goodman et al., 2018) to 12 (Dragoo et al., 2012) times higher during games than practice with type of injury varying by position, with factors like player contact, diving, and awkward landings being major causes (Tummala et al., 2018). Quarterbacks, defensive backs and linemen face higher risks for labral tears and instability than players at other positions (Goodman et al., 2018).

Cervical Injuries: The risk of cervical injuries in college football is low, with a rate of about 2.91 per 10,000 athlete exposures (Chung et al., 2019). Defensive linemen and linebackers were more frequently affected than players in other positions, and injuries were nine times more likely to occur with contact during games than practice (Chung et al., 2019; Lee et al.,2019). Furthermore, players with cervical spinal stenosis had a higher risk of experiencing stinger injuries, with a 2.98 OR compared to players without stenosis (Meyer et al. 1994).

Syndesmosis injuries refer to damage to the syndesmotic ligaments connecting the lower leg’s tibia and fibula bones. According to Hunt et al. (2013), the incidence of syndesmosis injuries in football was higher on artificial turf (.29 per 1,000 athlete exposures) compared to natural grass (.22 per 1,000 athlete exposures). Additionally, the study found that syndesmosis injuries were nearly 14 times more likely to occur during games compared to practices, mirroring the factors for more general injury risk among American football players.

Anterior cruciate ligament (ACL) injuries: Risk factors of ACL injuries included games (vs practice), artificial playing surfaces, and previous knee injuries.Risk of ACL injuries was 10.09 times higher during games than during practice. Playing on artificial surfaces was associated with 39% higher risk of injury compared to grass (Dragoo et al., 2012). According to Rahnemai-Azar et al. (2016), ACL injuries were associated with structural abnormalities such as increased lateral tibial slope (OR = 1.32), increased medial tibial plateau slope (OR = 1.42), narrower lateral femoral condyle (OR = .82), and increased lateral tibial plateau slope (OR = 1.43).

Knee Injuries: Knee injuries included medial collateral ligament (MCL) tears, meniscal injuries, and anterior cruciate ligament (ACL) tears and history of previous injuries was a major risk factor (Bradley et al., 2008; Loughran et al., 2019). Knee injuries were more frequent (two-fold higher) among defensive linemen and offensive linemen than players at other positions (Albright et al.,1994). Loughran et al. (2019) found that the risk of posterior cruciate ligament (PCL) knee injuries was 2.94 times higher on artificial surfaces than grass, whereas ACL injuries had 1.64 times higher risk on artificial surfaces. Moreover Smith et al. (2017) found that individuals who had undergone ACL reconstruction were at a 2.0 times higher risk of developing knee osteoarthritis.

Hand and wrist injuries: Both contact and overuse were significant contributory risk factors of hand and wrist injuries such as collateral ligament tears of the thumb, and fractures. Injuries were most frequent during regular practices and competitions, with higher risk among offensive and defensive linemen than players at other positions (Bartels et al., 2019).

Back injuries: Risk of back injuries was three-fold higher during games than practice (Makovicka, Chhabra, et al., 2019) and was often linked to poor technique, muscle imbalances, high training volume leading to muscle fatigue, and biomechanical issues like poor spinal alignment or movement patterns (Makovicka, Patel, et al., 2019; Makovicka, Chhabra, et al., 2019).

Fatalities: Risk of fatal injuries was primarily related to overexertion and underlying medical conditions (e.g., sickle cell trait) that are exacerbated by intense training (Begier et al., 2004; Boden et al., 2013). Moreover, most non-traumatic deaths occured during supervised, high-intensity conditioning sessions rather than during games. Boden et al. (2013) found that the risk of heat-related fatalities was 3.8 times higher in college compared to high school, with an average of .51 fatalities per year. Thsickle cell trait increased the risk of fatalities by 66.6 times in college compared to high school, with an average of .57 fatalities per year, whereas asthma increased the risk by 2.4 times, with an average of .06 fatalities per year (Boden et al., 2013).

Infections: Risk of inflections linked to close contact, skin trauma from turf burns or abrasions, sharing equipment and personal items like towels and water bottles, and poor hygiene practices was higher among cornerbacks (RR of 17.5) and wide receivers (RR of 11.7) than other players (Begier et al., 2004). Additionally, body shaving (RR of 6.1) and playing on artificial grass (RR of 7.2) were also associated with higher risk of infections (Begier et al., 2004).

Fractures: Risk of fractures was 10 times higher during games than practice (1.8 versus .17 per 100 athlete exposures) and was often linked to an athlete’s physical and biological characteristics (e.g., low/high body mass index, weak or fatigued muscles, history of fractures) or environment (e.g. playing on artificial turf) (Cairns et al., 2018).

Discussion

This review has systematically examined the literature on risk factors associated with injuries among NCAA football players, categorizing them by type. Overall, NCAA football related injuries are influenced by both intrinsic (athlete-specific) and extrinsic (environmental) factors. However, the specific risk factors differ by type of injury (concussions or brain injury, hip injury, lower extremity injury, stinger injury, turf toe injury, depression, elbow injury, shoulder injury, cervical injury, ankle injury, knee injury, hand and wrist injury, back injury, fatality, infection or sickness, and fractures). Athlete specific characteristics (such as age, history of injuries), behaviors (e.g., overtraining, high training intensity, or inadequate recovery), and environmental factors (such as type of competition [game vs practice] and artifical turf playing surfaces).

Games were consistently associated with a higher risk for injuries than practices, regardless of the type of injury. Gamesare more intense and competitive (Makovicka, Patel, et al., 2019). Consequently, athletes tend to put in more effort (e.g., overtraining, high training intensity) and engage in riskier behaviors (e.g., inadequate recovery time)to win. This raises the chances of sustaining injuries (Bartel et al., 2019;Wilkerson et al., 2016). Given the competitive nature of games, injuries might be inevitable, therefore, reinforccement of proper techniques for movements, tackles, and falls during games may help minimize players’ susceptibility to injury. In contrast to a NCAA football game, football practice is often light-contact or sometimes even a no-contact activity meant to teach skills and simulate games. Compared to games, practices were associated with a lower risk of injuries. Overall, across injury types, the risk of injury rose depending on the football season and type of competition. Spring practices were associated with the lowest risk of injury. During the spring, players are often training without an upcoming game. After the spring practices, the risk of injuries increased monotonically during fall practices, preseason games, and regular season games irrespective of type of injury.

The relationship between player age and risk of injury was complex, with both younger and older age groups having risk for different types of injuries. While older players had a higher all-cause risk due to factors like cumulative stress and reduced recovery, younger players were at greater risk for injuries like fractures, strains, and concussions. For young athletes, the repercussions of injuries, such as concussions, can have more profound long-term effects on cognitive development, academic performance, and mental well-being. Early and structured training could provide some safety for football players. In addition, age-appropriate tackling techniques, enforcement of stricter regulations, and potentially older age of football exposure could be viable preventive strategies to reduce the burden of football injuries.

Artificial turf was associated with higher risk of injuries than natural grass playing surface across all types of injuries. Turf is relatively poor in absorbing movement-related impact and tends to carry more friction that may cause a player’s feet to “stick” to the surface involuntarily. Turf also absorbs less impact than natural grass. Turf elevates the risk of turf toe, syndesmosis injuries, and practice injuries in general according to the literature. Although artificial turf requires less maintenance than natural grass, this maintenance benefit comes at a significant injury cost to football players. It is important to note, however, that the characteristics of the present turf technologies elevate lower extremity injury risks. However, this may not be the case for future turfs developed to absorb more impact and impose less surface friction.

Lower extremity injuries are highly prevalent, with over 50% of all reported injuries affecting the lower extremities, including hip, thigh, knee, lower leg, ankle, and foot. One potential reason for this could be the sudden changes in direction, abrupt stops, and explosive movements during gameplay. Additionally, ill-fitting footwear worn by some players may also play a role in lower extremity injuries. Shoes that lack proper support or traction can heighten the chances of falls and twisting injuries. Lower extremity injuries can range in severity and type, including sprains, strains, fractures, and dislocations. The more prevalent risk factors identified included playing on artificial turf, abnormal field conditions, and a history of concussion. To reduce these risks, athletes must engage in thorough warm-up routines to prepare their muscles and joints before playing. Furthermore, educating players on correct techniques for tackling, blocking, and other movements is essential.

Player characteristics such as playing position, age, experience, and physical fitness (e.g., dynamic balance) influence injury risk. Particularly, positions such as defensive backs and linebackers are associated with higher risk of injury. For these positions, physical limitations (poor balance and slow reaction time) are correlated with higher frequency of injuries. Contact at periods of poor balance can force a player into an abnormal and potentially injurious movement.Football involves rapid changes in play direction, unexpected tackles, and sudden stops. Proper balance allows players to tackle opponents more effectively and safely. When being tackled, balance helps them maintain a controlled posture, reducing the risk of injury from the impact. Similarly, faster player reaction time protects against lower extremity injury. Both faster reaction time and good balance are protective factors against injury, enabling players to anticipate and evade any potential abnormal bodily movements during contact. Moreover, prior injuries also impact player balance and reaction time and thus play a significant role in player’s risk for future injuries. There is a paucity of research on the association between negative life stress and injury risk; but a few studies suggest low levels of stress and family social support may be beneficial (Petrie et al., 2014).

In summary, the risk factors for NCAA football related injuries are interrelated and multifactorial inlcuding player characteristics and attributes (such as age, player position, experience, history of injuries, and physical fittness), training factors (like insufficient recovery, high-intensity workloads), and game-related factors (including increased exposure to contact and high-friction surfaces). To mitigate risk of football related injuries, establishing a safer environment for athletes by strengthening protective measures and reducing risk factors through comprehensive policy and rule changes is needed. These adjustments may involve reinforcing concussion protocols, mandating rest periods and return-to-play protocols, modifying rules to minimize high-risk plays, implementing rules that encourage safer play, creating awareness about the long-term health consequences of injuries, and various other measures.