Original paperNormative values of hip strength in adult male association football players assessed by handheld dynamometry
Introduction
Groin pain is a common problem in association football (soccer) players. Groin injuries account for up to 22% of injuries requiring time off training and out of competition.1 Acute strains of the groin may resolve in a short period of time but once the injury becomes chronic, it is often more difficult to manage.1 Symptoms may change with time, and more than one problem can develop.2 There is debate about the aetiology of adductor related groin pain with different authors suggesting a bone stress injury,3 an adductor enthesopathy, enthesitis,2 partial avulsion,4 or some form of inguinal fascial defect.5
With the aetiology unclear, there remains a need to manage athletes with chronic groin pain in order to help them to return to sport. Holmich et al. have shown that a structured strengthening programme is better at returning athletes with adductor related groin pain to their sports than physiotherapy without strengthening.6 Tyler et al. have shown that both absolute and weight-corrected weakness of the hip adductors are associated with an increased risk of groin injury in ice hockey players,7 and that strengthening of the adductors reduces this risk.8 Currently the normative strength values in association football players, and therefore the goals for rehabilitation are unknown.
Various authors have reported using simultaneous adductor activation tests to stress the adductors and the symphysis pubis in athletes who have adductor related groin pain. Holmich et al.9 evaluated a number of tests for assessing groin pain and showed that resisted hip adduction with hips and knees extended was reproducible and had minimal variability (Fig. 1A). Verrall et al.10 described the “Squeeze test” which is performed with the patient supine, hips flexed to 45° and knees at 90°, and squeezing on the examiner's fist (Fig. 1B). Rodriguez et al.11 described the “Pubic Symphysis Gap Test” which is performed with the patient supine, hips and knees flexed to 90°, feet off the plinth and again, squeezing the examiner's fist between the knees (Fig. 1C).
Other authors have used resisted hip flexion to stress the joints of the pelvic ring. Holmich et al.9 assessed the reliability of testing resisted hip flexion with the hip flexed to 90° and found that the greater strength of this muscle made this testing position less reliable than other tests. Tyler et al.7, 8 tested the strength of resisted hip flexion over the end of an examination couch (Fig. 1D). In this position, the hip is extended.
In a study that considered 24 different criteria that could be used to assess clinical improvement in athletes recovering from osteitis pubis, Hogan and Lovell12 reported that only five criteria were statistically significant. They included the absence of pain with isometric hip adduction in various degrees of hip flexion, and the absence of pain during the Modified Thomas Test. They recommend the use of these criteria in determining the appropriate time to progress load in athletes who are recovering from osteitis pubis.
Bohannon has stated that normative values of strength are essential in order for therapists to be able to correctly identify patients with physical limitations.13 He has shown that manual muscle testing does not have the sensitivity of handheld dynamometry for detecting deficits in strength relative to normal values.14
The aim of this study was to record the normative strength values in association football players, of the muscle groups commonly tested in the clinical assessment of athletes with groin pain, using handheld dynamometry in recommended test positions.
Section snippets
Methods
Adult male players from seven association football teams participating in the New Zealand Football Championship and Northern Premier League competitions within the Auckland region of New Zealand were invited to participate in this study. All players attending training sessions while testing was being conducted were included. Players were excluded if they were unable to fully participate in training as a result of injury at the time of testing. Written informed consent was obtained from club
Results
One hundred and twenty-one players from seven football teams were invited to participate in this study. All invited players agreed to participate (100%). One player withdrew due to the development of groin pain during testing. Therefore 120 (99%) participants completed the study. The age of participants ranged from 15 to 45 years (mean 24.9 years, SD 5.9), with the number of previous seasons played at this level ranging from 1 to 27 (mean 8.8, SD 6.3). Eighty participants (66.9%) had
Discussion
This study assessed the strength of adult male association football players. We present normative ranges of strength for hip muscle groups in testing positions commonly used in the assessment of adductor related groin pain. Regression equations have been provided to allow for the calculation of individual-specific strength of these muscle groups. This information can be used to assess the degree of an athlete's weakness at presentation relative to predicted normal. This information may be used
Conclusion
This study establishes reference ranges for strength of the hip muscles in adult male association football players. We have also shown that weight, playing position and employment type are associated with hip muscle strength and have provided predictive equations for hip muscle strength. This information can be used to monitor recovery from injury, and with further research may be useful in identifying athletes at risk of injury, and in the development of injury prevention strengthening
Practical implications
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The predictive equations calculated can be used to estimate normal hip flexor and adductor strength for association football players using information about their leg dominance, height, weight, playing position and work type.
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The predictive equations for hip muscle strength of adult male association football players may prove useful in return to play decisions following groin injury, identifying those at risk of injury and injury prevention programmes.
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There is a significant difference in hip
Acknowledgements
The authors would like to thank the players and clubs who participated in this study. There has been no financial assistance for this research project.
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