Welcome to the 9th edition of the Learn.Physio Research Review!
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Groin Injury Reduction
A research review by Learn.Physio
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After spending a few weeks down at the Achilles and ankle, let’s discuss hip-related and adductor-related groin pain in this issue of Learn.Physio Research Reviews!
Semi-professional and community/school level soccer and AFL competitions are about to kick off here in Australia, so I want to share with you a tremendous research paper that showed the addition of 1 simply exercise to the weekly training environment reduced the prevalence of in-season groin complaints by 40%!
The second paper I want to share with you is one that identified lower levels of hip adductor and abductor strength, and subjective questionnaire responses, as measured at the start of pre-season, were associated with higher chances of in-season injury.
For some of you, it may be a little bit too late to introduce these pre-season exercises and screening tools for this upcoming season, but I’m you’ll find valuable take home messages from these papers that can change your clinical practice, and help your patients and athletes, in the future!
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Introduction
Groin injuries represent a considerable problem in male soccer/football players, and accounts for 4-19% of all time-loss injuries. To combat common time-loss injuries, such as groin injury in soccer/football players, the FIFA 11+ injury prevention program was developed, and it has been shown in 2 studies that the 11+ has a preventative effect on hip and groin injuries – albeit in males soccer/football players only.
In previous work in soccer/football, low hip ADDuction strength has been identified as an important and modifiable risk factor associated with increased risk of groin injury. Furthermore, >20% deficit in eccentric strength of the hip ADDuctor muscles has been observed among players with groin pain. Thus it seems reasonable to think that strengthening the adductor muscles plays an important role in reducing the prevalence and rate of groin injuries in soccer/football athletes.
The Copenhagen Adductor strengthening exercise has been identified as a high value exercise in football players due to its high activation of adductor longus, and its ability to elicit a considerable eccentric muscle contraction. It also does not require any equipment to perform the exercise - just a partner or a bench/chair.
The purpose of this randomised controlled trial was to test the effect of a single exercise approach (Copenhagen Adductor exercise) to reduce the prevalence of groin complaints in male soccer/football players.
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Methods
During a soccer/football pre-season (Feb and March), semi-professional soccer/football teams in Norway were invited to participate in this study. All teams/players who agreed to participate in this study were randomised to either an “intervention” group or a “control” group and followed until the end of the competitive season in October.
Basic demographic data was captured by the authors as well as playing position, dominant leg and years playing in senior football. Players also recorded their current hip and groin symptoms via the Oslo Sports Trauma Research Centre (OSTRC) overuse injury questionnaire, and the Copenhagen Hip and Groin Outcome Score (HAGOS) at baseline.
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Intervention:
The Copenhagen Adductor (CA) strengthening programme consisted of a single exercise with 3 levels of difficulty. As the CA might be painful, or difficult to do in symptomatic players (or players who are weak in the adductors), two easier options were created from the authors of the paper.
Level 3 – standard CA exercise
Level 2 - moderate CA exercise
Level 1 - easy CA exercise
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Players were asked to start at level 3 CA exercise, however if they experienced pain >3/10, they were instructed to perform level 2 CA exercise. Similarly, if level 2 provoked pain >3/10, there were instructed to perform level 1 CA exercise.
Note: whatever level of exercise was to be performed, it was performed on both legs.
Teams in the intervention group were asked to perform the exercise as part of their “usual” warm-up 2-3x per week for a minimum of 6 weeks during the pre-season, and maintain the programme 1x per week throughout the regular season. The control group did their “usual” warm-up and training practices without the CA exercise.
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Outcome Measures
The primary outcome measure was the prevalence of all groin problems registered during the competitive season (28 week season) using the OSTRC overuse injury questionnaire.
“Groin problems” was categorised as any hip or groin symptoms including pain, ache, stiffness, clicking/catching or other complaints related to the groin, or if they reduced training participation, volume or performance due to groin problems.
The secondary outcome measure was the weekly prevalence of substantial groin problems registered during the competitive season
“Substantial” groin problems were identified as moderate or severe reduction in training volume or football performance, or a complete inability to participate due to groin problems.
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Results:
A total of 35 teams (652 players) were enrolled in the study; 247 players randomised to intervention group and 242 players randomised to control group.
At baseline there were no group differences in the prevalence of groin problems or any of the HAGOS subscales. Important to note that both the intervention and control groups each had 32% of their players reporting “groin problems” at the start of pre-season and 12-13% reporting substantial groin problems at the start of pre-season.
There were no differences in exposure to football training, individual training, match minutes or number of games played during the competitive season between the intervention and control groups.
For the primary outcome of “all groin problems”, the average weekly prevalence during the competitive season was 13.5% in the intervention group and 21.3% in the control group – that reflects a statistically significant 41% lower risk of reporting groin problems in the intervention group compared to the control group.
For the secondary outcome measure of “substantial groin problems”, the average weekly prevalence during the competitive season was 5.7% in the intervention group and 8.0% in the control group – that reflects a non-significant 18% lower risk of reporting a substantial groin problem in the intervention group compared to the control group.
Compliance to the CA programme was also observed throughout the pre-season and competitive season and the authors found that 73% of the players conducted the CA strengthening programme as recommended during the pre-season. During the competitive season, this dropped slightly to 70% of the recommended CA programming.
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Discussion:
This was the first study investigating the effects of a single-exercise approach (CA) to reduce the prevalence of groin problems in football players – with the main finding being that CA strengthening started in the pre-season and maintained throughout the competitive season, reduced the prevalence of in-season groin problems amongst semi-professional, adult male soccer/football players by 41%.
A possible explanation of such tremendous reductions in groin problem prevalence was the simplistic nature of the intervention (one exercise and its modifications, that requires no equipment, and takes less than 5mins to perform) and simple maintenance program throughout the competitive season.
It is no doubt that this tremendous result was assisted by high adherence rates throughout the pre-season and in-season (70%-73%). Compared to other studies that have observed compliance rates in groin injury prevention programs (combination of both static and dynamic groin exercises as well as abdominal exercises), others have found compliance as low as 19% (Engebresten et al 2010).
From an exercise prescription standpoint, the authors acknowledged that there is still an unknown as to what the optimal dosage for the CA strengthening program. Note that the program was only prescribed 1 set per side - with progressive rep ranges and frequency per week over the course of the programming. However, what is unknown is, would there be more of a reduction in groin problem prevalence with 2-3 sets per week? Alternatively, how many sets and reps per week is too much that it then impairs training/game availability and performance?
Another important thing to note was that no players reported any adverse events in response to this exercise intervention, and players reported very low level of delayed onset of muscle soreness (DOMS) whilst performing this exercise. The highest levels of DOMS reported in this study was observed in the start of pre-season when training was resumed, and all players observed an increased load of football training. So, to blame the DOMS at the start of the pre-season training on the CA exercise, needs to be carefully considered.
A key limitation to this trial and the effect of the CA exercise programme is that the programme targets only 1 of the 5 entities for groin pain (adductor-related groin pain). Although adductor-related groin pain accounts for 2/3 of all hip and groin pain in football/soccer athletes, it is unknown whether the CA exercise has a positive influence on other entities; such as pubic-related groin pain, hip flexor-related groin pain, abdominal-related groin pain or hip-related groin pain.
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Summary
Although we are yet to know the “optimal dosage” of CA strengthening exercises and whether the results of this trial would be observed in adult females and younger male and female soccer/football players, this randomised controlled trial on semi-professional male soccer players showed that simply performing the CA strengthening exercise in a progressive manner throughout a pre-season, and then maintained throughout an in-season, was effective in reducing groin problems by 41%.
To have this profound and significant effect on a very common football/soccer injury that impairs training/playing availability and both individual/team performance with 1 exercise, that takes less than 5mins to complete, and requires no equipment, is a game-changer - and I strongly urge all physiotherapists, exercise professionals, sports trainers, coaches, parents, administrators and players to look to implement this simple, yet highly effective exercise into the weekly training environment.
The possibility of this simple exercise program to be generalised to other sporting codes that also have a relatively high prevalence of groin complaints such as Australian Rules Football (AFL), Rugby or Ice Hockey is also worth exploring, considering the ease of its application.
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If you're enjoying this research review check out Dr Joanne Kemp & Dr Sue Mayes's new Masterclass: The High Performance Hip
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Introduction:
Consistent with what was discussed in article #1, around 20% of soccer/football players will sustain a hip/groin injury in any given season, and approximately 30% of injuries will re-occur. These figures however are likely to be under-represented to the true prevalence of hip/groin pain in soccer/football athletes, as many continue to train and play despite symptoms.
Lower isometric and eccentric hip adduction strength has been associated with an increased risk of hip/groin injuries in male soccer/football players; and athletes with groin pain also have lower isometric adductor strength than asymptomatic athletes. Given that the onset of groin injury and recurrence may be related to reduced adductor strength, it is possible that deficits or between limb imbalances in hip adductor strength may be associated with injury.
No study to date has explored isometric hip adduction strength and future hip/groin injury; however previous work has looked at concentric and eccentric hip adduction strength with conflicting results. Which is why the authors of this study aimed to find out whether pre-season hip adductor and hip abductor strength (and between limb differences) and HAGOS values were associated with clinically diagnosed hip/groin injury in the subsequent season in professional soccer players?
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Methods:
This prospective cohort study was conducted during the 2017-18 A-league and English Championship League competitions. 204 elite male athletes (mean age 24.5yrs) from 9 A-league clubs and 1 English Championship League club consented to be part of this study.
On a single day at the start of pre-season training players were asked to complete the HAGOS questionnaire and a standardised questionnaire detailing demographic data, limb dominance, playing position and history of lower limb injuries. Players also had their isometric hip adduction and abduction strength assessed using the Groinbar strength testing device (Vald Performance).
Isometric strength testing:
Strength testing was carried out in supine, with hip adduction and adduction measured in 2 positions:
- From the ankle with hip in neutral and knees extended (biasing adductor longus)
- From the knee with the hip at 60deg flexion and knee at 90deg flexion (biasing short adductors)
In each position, participants performed 1 set of 3rep maximal voluntary hip adduction contractions (10sec rest between reps), followed by 1 set of 3rep maximal voluntary isometric hip abduction contractions (10sec rest between reps).
Participants had 30sec rest between sets, and at least 1min rest between each testing position.
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Injury reporting:
A hip/groin injury was defined as “an injury located to the hip joint of surrounding soft tissues, or at the junction between the anteromedial part of the thigh, that resulted from playing football, and led to the player being unable to fully participate in future training or match play”.
For all injuries that satisfied this inclusion criteria, team medical staff completed a detailed standardised injury report covering many aspects about time of injury, location of injury, number of training sessions/matches missed, grade of injury, side of body, recurrence, any imaging required, mechanism of injury etc.
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Results
Complete data was obtained from 152 players (52 lost to follow-up due to missing on incomplete pre-season data). At baseline there were no differences in demographic data, HAGOS and strength values for players lost to follow-up and the remainder of athletes with complete data.
During the subsequent competitive season, 24 out of the 152 players analysed sustained at least 1 hip/groin injury. Most injuries were mild and resulted in on average 1.7 games missed, 6.5 missed training sessions and 2.2 modified training sessions.
67% of the injuries were adductor-related, 17% iliopsoas-related and 8% were inguinal-related and 66% affected the non-dominant limb.
The key findings in regard to sustaining a future hip/groin injury based on pre-season isometric hip adduction and abduction strength tests and HAGOS scores are as follows:
- increased risk when lower peak hip adduction and abduction strength
- lower HAGOS scores
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Discussion
This study has demonstrated 2 key features that highlight a lower chance of sustaining a future hip/groin injury in professional soccer players:
- increased hip adductor and abductor strength
- high HAGOS values
Consistent with what was reported in Haroy et al (2019) above, this study also showed that high levels of hip adduction strength (and abductor strength) were somewhat protective of a future hip/groin complaint in the future.
These 2 papers (and the work from Engebresten et al 2010 who showed 4x more likelihood of sustaining a future hip/groin injury with weak adductors) further strengthens the need to incorporate hip adduction strength and hip abductor strengthening into injury prevention and rehab programs in soccer/football players.
What was not quite made clear for interpretation was “what was high levels of strength” in both the abductors and adductors? Given that not every clinician will have access to a Groinbar for strength testing, hand-held dynamometry is an alternative that some clinicians may have access too.
Dr Joanne Kemp speaks about high standards that she sets for her hip/groin athletes with hand-held dynamometry in our High Performance Hip Masterclass; with a bare minimum being 150N on each limb and an 1:1 ratio of adductor strength to abductor strength also being a target.
In respect to the HAGOS, the players in this group were 23% less likely to have a hip/groin injury in the subsequent season when they had “high” HAGOS scores compared to those who “low” HAGOS scores.
Once again, it was not clear what was defined as “high” and “low”, but the authors did report that their findings are consistent with Delahunt et al (2017) who showed that athletes who scored <87.5 on the “function, sport and recreation subscale of the HAGOS were 9x more likely to sustain a groin injury than those with scores >88.
Given that the HAGOS outcome measure’s maximal score is 100; it would be fair to say that we would be looking for scores 90 or above on all subscales of the HAGOS questionnaire; and those players who scored >90 would likely have less chance of sustaining a future hip/groin injury in the future. Thus, the HAGOS outcome measure would be an important tool to be utilising in both pre-season screening and in-season monitoring of players with hip/groin complaints.
As the authors mention in their limitations section, a key limitation to this study is the limited generalisability of this data from an elite professional environment to a sub-elite standard of football, or a female population of soccer/football athletes, or even other athletic populations such as AFL or Ice-Hockey who also have relatively high incidence and prevalence of hip/groin complaints.
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Conclusion
Given that we know lower levels of isometric hip adduction and hip abduction strength are modifiable risk factors to the onset of future hip/groin pain, no matter the level of soccer/football athletes (or the sex of the athlete), screening your players in the pre-season for strength may shed some light on who you may target for added hip adduction and abduction strength to keep them on the paddock consistency throughout the year. Screening your athletes also via the HAGOS (and looking for lower scores below 90) would also be a useful tool to identify those that may also need some target hip adduction and abduction strengthening intervention as well.
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We know that groin strengthening is an integral part of Groin Rehab. Learn the progressions, the exercises and the framework in Jo Kemp & Sue Mayes's New Masterclass, The High Performance Hip
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References
Harøy J, Clarsen B, Wiger EG, Øyen MG, Serner A, Thorborg K, Hölmich P, Andersen TE, Bahr R. The Adductor Strengthening Programme prevents groin problems among male football players: a cluster-randomised controlled trial. Br J Sports Med. 2019 Feb;53(3):150-157. doi: 10.1136/bjsports-2017-098937. Epub 2018 Jun 10. PMID: 29891614.
Engebretsen AH, Myklebust G, Holme I, Engebretsen L, Bahr R. Intrinsic risk factors for groin injuries among male soccer players: a prospective cohort study. Am J Sports Med. 2010 Oct;38(10):2051-7. doi: 10.1177/0363546510375544. Epub 2010 Aug 10. PMID: 20699426.
Bourne MN, Williams M, Jackson J, Williams KL, Timmins RG, Pizzari T. Preseason Hip/Groin Strength and HAGOS Scores Are Associated With Subsequent Injury in Professional Male Soccer Players. J Orthop Sports Phys Ther. 2020 May;50(5):234-242. doi: 10.2519/jospt.2020.9022. Epub 2019 Sep 17. PMID: 31530069.
Delahunt E, Fitzpatrick H, Blake C. Pre-season adductor squeeze test and HAGOS function sport and recreation subscale scores predict groin injury in Gaelic football players. Phys Ther Sport. 2017 Jan;23:1-6. doi: 10.1016/j.ptsp.2016.07.002. Epub 2016 Jul 9. PMID: 27636987.
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Thanks for reading and staying up to date. I look forward to sharing more in the future.
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