Risk Factors for Athletic Pubalgia in Collegiate Football Student-Athletes: A Retrospective Cohort Study

Abstract

Background:

Athletic pubalgia (AP) is an increasingly recognized injury among young athletes. This study aimed to evaluate the characteristics associated with AP in college football players.

Hypothesis:

Repetitive explosive movements that require aggressive core muscle activation results in AP in collegiate football players.

Study Design:

Retrospective cohort design.

Level of Evidence:

Level 3.

Methods:

Football student-athletes at a single Division I collegiate institution from January 2010 to December 2019 were included in the study. The primary outcome measure was surgery for AP. The odds of AP were determined using logistic regression, with the dependent variable being whether or not the student-athlete received AP surgery. Independent variables included Olympic weightlifting (OWL) exposure, primary playing position (skill position vs nonskill position), and body mass index (BMI).

Results:

A total of 1154 total student-athlete exposures met the inclusion criteria. Of the 576 student-athletes exposed to OWL (OWL occurred throughout entire calendar year), 20 developed AP, whereas 7 student-athletes not exposed to OWL (OWL was not performed at any point during calendar year) developed AP. Student-athletes exposed to OWL had a 2.86 (95% CI, 1.25-7.35; P = 0.02) times higher odds of AP than players not exposed after controlling for primary playing position and BMI. Skill position players had a 9.32 (95% CI, 1.71-63.96; P = 0.01) times higher odds of AP than nonskill position players when controlling for BMI and OWL training.

Conclusion:

Modifiable factors that increase exposure to repetitive explosive activities, such as OWL and playing a skill position, may be important considerations in developing AP.

Clinical Relevance:

The cause of AP is multifactorial and poorly understood. Identifying factors associated with AP informs athletes, athletic trainers, physicians, and coaches.

Athletic pubalgia (AP), also referred to as “Gilmore’s groin” or inguinal disruption,^35,42 is a common cause of chronic groin pain, accounting for up to 28% of groin injuries among athletes.^11,27 While this injury has also been described as a “sports hernia,” the description is vague and commonly replaced with more specific terms to describe the injury accurately. ⁹ An imbalance of adduction and abduction forces, centered on the pubic symphysis, is purported to result in an insertional shearing of the common aponeurosis of the rectus abdominis and adductor longus attachments to the pubic bone. ²⁵ Similarly, AP may also involve the inguinal canal, causing weakening of the posterior wall. ³⁸ Previous research suggests that AP occurs during sporting activities that require sudden direction changes, accelerated twisting, or explosive movements. ⁶ Indeed, a retrospective case series of National Hockey League athletes found that the incidence of AP injury is increasing among elite male athletes. ¹⁰ Similarly, a study examining the MRI of Australian male football players found a large proportion had evidence of groin injury. ⁴¹ Hip and groin pain accounts for up to 6% of all athletic injuries.^17,29 Although most athletic groin injuries resolve with nonoperative management and do not evolve into AP, injuries persisting more than 3 months without significant improvement are associated with an increased likelihood of requiring surgical intervention.^7,26

More recently, several authors have demonstrated an association of AP in athletes and limited hip motion.^14,20 For example, Larson et al ¹⁹ reported improved outcomes in athletes who underwent concomitant AP surgery and arthroscopic hip surgery to treat underlying femoroacetabular impingement (FAI). Similarly, Hammoud et al ¹⁴ found a high incidence of AP in professional athletes with symptomatic FAI syndrome. Schilders et al ³³ demonstrated the effectiveness of selective partial adductor release in professional athletes for groin pain, suggesting that proximal adductor injury is essential to AP injury. Although a recent meta-analysis found that surgical treatment of groin-related pain in athletes resulted in improved outcomes than conservative management, the number of high-quality studies is limited. ³⁴ Evaluating athletic groin-related pain is challenging, and recommendations rely on smaller case series or expert opinion. ⁸ As a result, the average patient sees more than 3 providers before arriving at a proper diagnosis. ³² Indeed, improved understanding of sport-related risk factors for AP offers the potential to identify the constellation of findings seen in AP accurately, prevents the need for surgical treatment, and minimizes the time away from sport.

This study aimed to evaluate the effect of Olympic weightlifting (OWL), body mass index (BMI), and position type (skill vs nonskill) among elite collegiate football players with respect to the development of AP. We hypothesized that activities requiring repetitive explosive core muscle activation result in an increase of AP development.

Methods

Data Collection

The study design was a retrospective cohort study of a single National Collegiate Athletic Association (NCAA) Division I football team between the 2010 and the 2019 seasons. Data analyzed included age, height, weight, BMI, primary position, FAI syndrome, and OWL participation. The player’s primary position was categorized as a skill or nonskill position. Skill positions were defined as quarterbacks, wide receivers, running backs, tight ends, linebackers, cornerbacks, and safeties. These positions were subject to a high volume of running, cutting, and rapid change of direction. Nonskill positions were defined as offensive linemen, defensive linemen, and specialists (punters, kickers, and long snappers), with these positions being subject to typically a lower volume of running, cutting, and activities involving rapid change of direction.

OWL consists of 2 lifts: the clean and jerk, and the snatch. The snatch is completed in 1 consecutive movement where the lifter pulls the barbell from a platform with a wide grip to a fully extended position overhead (Appendix Figure A1, available in the online version of this article). The clean and jerk is completed in 2 phases, with the first including a pull from the platform in a narrow grip to a standing position and the second including an explosive vertical press overhead (Appendix Figure A2, available online). OWL training was universally instituted for team conditioning in January of 2015. Therefore, all student-athletes from the 2015 roster onward were exposed to OWL training. The primary outcome measured was surgery for AP.

All athletes who presented with pubic, groin, or abdominal pain were evaluated clinically by the team orthopaedic surgeon and head athletic trainer. Criteria for clinical diagnosis included tenderness to palpation of the proximal adductor or rectus abdominis muscle, pain with long lever test on adduction, positive sit-up test with pain at the level of core muscle insertion, and inability to progress through sport due to pain (typically from sprinting). The long lever test on adduction involves placing the student-athlete in a supine position with the hip in 30° of flexion. With the knee fully extended, the student-athlete is then asked to resist adduction. Pain on this maneuver defines a positive test. MRI confirmed the diagnosis. Major MRI characteristics included either rectus abdominis and/or adductor tearing from the aponeurosis and edema in the injured muscles (Appendix Figure A3, available online). Surgical treatment included an open surgical approach with repair of the rectus abdominis aponeurosis to the pubic bone. When indicated, decompression of the adductor compartment and tendon repair was also performed. An anterolateral release of the epimysium of the adductor fascia was utilized to alleviate inflammation. Previous core muscle injury or AP surgery excluded student-athletes from the study. Incidence of AP injury was obtained for each athletic year along with cumulative counts of AP surgery pre- and post-OWL exposure. The Institutional Review Board approved this study.

Statistical Analysis

Data are presented as means and standard deviations for continuous variables and counts (%) for categorical variables. Between-group means were compared with the Student t test for continuous variables. Categorical variables were compared using a chi-square test with Yate’s continuity correction. Univariate estimates were calculated using binomial logistic regression with AP as the dependent variable. The model estimates were adjusted for OWL exposure, primary player position, and BMI. A P value <0.05 was the threshold for determining statistical significance. Statistical analysis was performed using RStudio Team software. ³⁰

Results

A total of 1154 student-athlete exposures met the inclusion criteria, defined as any male football student-athlete listed on the active program roster and participating in football team activities from the 2010 through 2019 seasons. None of the student-athletes were excluded because of previous AP. A total of 27 student-athletes (2.34%) had AP surgery between the 2010 through 2019 seasons. Of the student-athletes who underwent AP surgery, 26 returned to play, whereas 1 student-athlete who received AP surgery at the end of his career did not return to play. The incidence rate of AP in this cohort was 20.5 per 1000 athlete-seasons. A total of 566 student-athletes were exposed to the OWL training (OWL occurred throughout entire calendar year), and 570 student-athletes were not exposed to the OWL training (OWL was not performed at any point during calendar year). Of the 27 student-athletes who underwent AP surgery, 12 were African American and 15 were Caucasian. A total of 3 athletes with AP had arthroscopic hip surgery to treat FAI: 1 athlete who had hip arthroscopy later developed AP, and 2 athletes with AP eventually required hip arthroscopy. The demographic data of all the athletes are summarized in Table 1. The demographic characteristics of athletic OWL participation were similar.

Table 1.

Comparison of demographic characteristics of collegiate football student-athletes by OWL exposure, 2010-2019 ^a

	OWL Exposure
Parameter	Yes (n = 566)	No (n = 570)	P Value
BMI, kg/m2	29.97 ± 4.49	29.83 ± 4.44	0.62
Height, m	1.88 ± 0.07	1.88 ± 0.07	0.69
Weight, kg	106.55 ± 20.89	106.23 ± 20.78	0.79
Skill position b			0.60
Yes	413 (73.0)	407 (71.4)
No	153 (27.0)	163 (28.6)

^aData represent mean ± SD or counts (percentages).

^bSkill positions include quarterbacks, wide receivers, running backs, tight ends, linebackers, cornerbacks, and safeties. Nonskill position include offensive linemen, defensive linemen, and specialists (punters, kickers, and long snappers).

BMI, body mass index; OWL, Olympic weightlifting.

A total of 820 student-athletes played primarily a skill position (Table 2). Demographics of skill position student-athletes between those athletes exposed to OWL and those that were not exposed to OWL training were similar. In all, 316 student-athletes played primarily a nonskill position (Table 3). Demographics of nonskill position student-athletes were likewise similar between those athletes exposed to OWL and those who were not exposed to OWL.

Table 2.

Comparison of demographic characteristics of student-athletes playing a skill position by OWL exposure, 2010-2019 ^a

	OWL Exposure
Parameter	Yes (n = 413)	No (n = 407)	P Value
BMI, kg/m2	27.74 ± 2.45	27.59 ± 2.44	0.37
Height, m	1.86 ± 0.06	1.86 ± 0.06	0.98
Weight, kg	95.72 ± 11.09	95.11 ± 10.00	0.40

^aData represent mean ± SD; Skill positions include quarterbacks, wide receivers, running backs, tight ends, linebackers, cornerbacks, and safeties.

BMI, body mass index; OWL, Olympic weightlifting.

Table 3.

Comparison of demographic characteristics of student-athletes playing a nonskill position by OWL exposure, 2010-2019 ^a

	OWL Exposure
Parameter	Yes (n = 153)	No (n = 163)	P Value
BMI, kg/m2	36.00 ± 2.93	35.43 ± 3.17	0.10
Height, m	1.94 ± 0.04	1.95 ± 0.05	0.49
Weight, kg	135.60 ± 10.91	134.02 ± 13.31	0.25

^aData represent mean ± SD; nonskill position include offensive linemen, defensive linemen, and specialists (punters, kickers, and long snappers).

BMI, body mass index; OWL, Olympic weightlifting.

We then examined the 27 student-athletes who underwent AP surgery; of these, 7 developed AP before exposure to OWL in 2015, whereas 20 developed AP after exposure to OWL (Figure 1). All student-athletes with AP participated in OWL training or played a skill position. There was no AP in student-athletes who were not exposed to OWL training and played a nonskill position. A total of 24 student-athletes (88.9%) with AP played a skill position compared with 3 nonskill position student-athletes (11.1%). The positions with the highest number of student-athletes with AP were wide receiver and cornerback (Figure 2). Of the 24 skill position student-athletes with AP, 17 (70.8%) student-athletes participated in OWL training. All 3 (100%) nonskill position student-athletes with AP participated in OWL training.

Figure 1.

Number of AP cases by year. Bar graph illustrating an increase in the number of AP cases in recent years. OWL was instituted in January 2015. AP, athletic pubalgia; OWL, Olympic weightlifting.

Figure 2.

Number of AP cases by position. Bar graph demonstrating the breakdown of AP cases by primary player position. Skill positions included quarterbacks, wide receivers, running backs, tight ends, linebackers, cornerbacks, and safeties. Nonskill position included offensive linemen, defensive linemen, and specialists (punters, kickers, and long snappers). AP, athletic pubalgia.

Student-athletes who participated in OWL training had an increased odds of AP compared with student-athletes who did not participate in OWL training (Table 4). Athletes exposed to OWL training had 2.95 times higher odds of AP than those athletes not exposed to OWL on univariate analysis (P = 0.02). Similarly, when controlling for playing a skill position and BMI, athletes exposed to OWL training had 2.86 times higher odds of AP than those athletes not exposed to OWL (P = 0.02). Student-athletes playing a skill position had 3.15 times higher odds of AP compared with student-athletes playing a nonskill position, and this approached statistical significance (P = 0.06) with univariate analysis. However, the mean BMI of skill position players was less than nonskill position players (27.67 kg/m² vs 35.71 kg/m²; P ≤ 0.01). Therefore, controlling for the difference in BMI between student-athletes playing a skill position compared with student-athletes playing a nonskill position, student-athletes playing a skill position had 9.32 times greater odds of AP compared with student-athletes playing a nonskill position (P = 0.01).

Table 4.

Estimated odds ratios for developing AP: results of a logistic regression analysis of collegiate football student-athletes, 2010-2019 ^a

Parameter	OR	95% CI	P Value
Univariate
OWL training	2.95	1.29, 7.56	0.02
BMI	0.97	0.89, 1.06	0.56
Skill position	3.15	1.09, 13.30	0.06
Adjusted
OWL training	2.86	1.25, 7.35	0.02
BMI, kg/m2	1.14	0.98, 1.33	0.09
Skill position	9.32	1.71, 63.96	0.01

^aAdjusted data: AP (yes/no) ~ OWL + BMI + skill position.

AP, athletic pubalgia; BMI, body mass index; OWL, Olympic weightlifting; OR, odds ratio.

Discussion

AP is a poorly understood condition that affects primarily high-level competitive male athletes and is associated with repetitive explosive movements that cumulatively injure the groin and surrounding tissues.^{1,13,19,22,23,36,37,40} Although AP surgery is associated with a high return-to-play rate, those who undergo AP surgery are more likely to have a shortened playing career. ⁴ By identifying risk factors for the development of AP, athletic programs may consider tailoring these modifiable factors to possibly mitigate injury. Recognition and a better understanding of this injury may increase the opportunity for athletes to enjoy healthy, successful careers. ²⁴ Here, we evaluated the effect of OWL, BMI, and position type (skill vs nonskill) among elite collegiate football players with respect to the development of AP. Indeed, we found that repetitive explosive movements requiring aggressive core muscle activation, namely participation in OWL and playing a skill position, resulted in an increased odds of AP. Explosiveness through the hips is especially important in OWL as the second pull occurs at this level. This movement places significant forces across the groin. ¹⁵ Our study supports the view that AP often occurs when the core muscles are activated in a forceful, eccentric movement. If the acute injury is not treated correctly or fails to heal sufficiently, it may develop into a chronic condition. ⁷

OWL is popular among strength coaches to help increase an athlete’s overall power. ¹⁶ Poor lifting form can translate to an imbalance of forces centered on the pubic symphysis. ⁴³ This imbalance in forces can place increased shear stress across the pubic symphysis leading to excessive load and eventual failure of the opposing muscles or aponeurotic attachments. ²¹ Indeed, chronic repetitive torque on the pubic symphysis may eventually result in avulsion of the common aponeurosis of the rectus abdominis and adductor longus tendons. ²⁸ It has also been hypothesized that off season training programs can further increase the imbalance in strength between stronger adductor muscles and relatively weak lower abdominal muscles. ²⁸ This has been supported by studies showing that adductor strains were 20 times more likely in hockey training camps than during the regular season. ⁵ Calhoon and Fry ³ reported that 30.4% of injuries among weightlifters were chronic in nature. Raske and Norlin ³¹ reported that 25% of weightlifting injuries were due to overuse of tendons. Collegiate football players are especially susceptible to chronic overuse injuries as they are exposed to strenuous practices and concurrent strength training throughout a collegiate football season. In addition to a 4-week training camp in August and football season that, on average, lasts 4 months, student-athletes also undergo focused training in the off season during the winter and summer months. Student-athletes did not compete in other sports during their collegiate career. With this in mind, player workload and weightlifting dosing frequency should be monitored to possibly prevent chronic overuse injuries.

OWL requires greater core muscle strength and dynamic body balance than more traditional forms of weightlifting. ² It has been shown that novice Olympic weightlifters have decreased dynamic balance and core muscle endurance compared with experienced weightlifters. ⁴³ Although the participants in our study were Division I college football players, it is important to recognize that few had significant training in OWL technique before exposure. This is relevant because, as the novice lifter fatigues during a workout, core muscle endurance and lifting technique will be negatively impacted. Because OWL requires explosive movements through the hips, a fatigued athlete with poor technique will likely place significant shear stress across their pubic symphysis during these movements. An athlete learning to perform Olympic lifts should undergo focused core stability training as this has been shown to improve core muscle endurance and dynamic balance. ³⁹

An interesting result from our study was that playing a skill position was strongly associated with an increased risk of AP. It has been shown that sports utilizing proximal thigh and lower abdominal muscles while also requiring significant pivoting and cutting can increase a player’s risk for AP. ³⁸ Our study agrees with this association and showed that student-athletes subject to the highest volume of running and cutting (wide receivers and cornerbacks) subsequently had the highest rate of AP injury, highlighting the need for interventions to mitigate risk among young athletes. Unlike other injuries involving the shoulder or knee, there is a relative paucity of protective equipment available to help prevent or minimize pelvic injuries. Because football requires a high degree of pelvic mobility, pelvic supports that limit movement are generally not a feasible option. Strength programs may consider a stronger emphasis on core and abdominal strength in their workout programs to help lower a student-athlete’s risk of AP. Increased hip mobility, functional core strengthening, proper warm ups, and strengthening of the hip flexor and groin muscles eccentrically are all strategies that may be utilized to help prevent AP. ¹² We also recognize the positive aspects of OWL on student-athlete development and do not recommend that these lifts be completely discontinued from weight training programs. Instead, our study demonstrates that further research is required to better define the constellation of findings seen in AP to correctly identify and prevent injury among those at an increased risk.

Limitations

Because AP is relatively uncommon, a larger population of student-athletes is needed to clarify the association between AP and training characteristics. Furthermore, we could not identify athletes who successfully resolved football-related pubalgia with conservative measures or sought treatment after graduation. However, surgical treatment of AP served as a sufficient endpoint for our study as refractory AP is almost always treated with surgical intervention. ¹⁸ The NCAA has strict guidelines on total practice time for student-athletes each week, making it unlikely that differences in time spent in practice or workouts confounded our study. Total practice hours and allotment of practices involving full protective equipment (helmet, shoulder pads, and thigh/knee pads) throughout a season are also capped by the NCAA and provide little room for variation. Methods of injury prevention incorporated into team practice routines may have varied depending on each coach’s training philosophy. Because OWL is becoming more popular among strength coaches, it is possible that more student-athletes in the exposure group were performing OWL in high school when compared with the control group. This early exposure could predispose a student-athlete to the development of AP while competing at the collegiate level.

Furthermore, AP may have historically been underdiagnosed because AP is a poorly understood injury. ¹⁹ The diagnosis of AP is increasingly recognized, raising the possibility that AP was evaluated more comprehensively and treated more aggressively in recent years. However, the diagnosis and treatment of AP was the same during this time period. While this study is retrospective, the research design allows an opportunity to understand relatively uncommon etiologies such as AP. Indeed, identifying pertinent and potentially modifiable risk factors is necessary for the vertical advancement in the understanding, treatment, and primary prevention of AP.

Conclusion

Modifiable factors that increase exposure to repetitive explosive activities, including OWL and primary position, may be important considerations in developing AP in college football players. Skill position players may benefit from modified training regimens to decrease this risk.