Elsevier

Physical Therapy in Sport

Volume 35, January 2019, Pages 63-68
Physical Therapy in Sport

Original Research
A novel device to assess hip strength: Concurrent validity and normative values in male athletes

https://doi.org/10.1016/j.ptsp.2018.11.006Get rights and content

Highlights

  • New novel device (GroinBar) correlates well with hand-held dynamometry for hip strength testing.

  • Normative values for male Australian rules football and football (Soccer) players identified.

  • No differences in strength found between those with and without past history of groin pain.

Introduction

Hip and groin problems are common in athletes, can impact on player ability, and may result in persistent pain and motor deficits (Mosler et al., 2018; Werner, Hagglund, Walden, & Ekstrand, 2009; Whittaker, Small, Maffey, & Emery, 2015). The assessment of hip adductor strength (both as an isolated measure and relative to abductor strength) is advocated for the identification of at-risk athletes (Thorborg et al., 2011a, 2014; Thorborg, Holmich, Christensen, Petersen, & Roos, 2011) and for early detection of groin problems (Crow et al., 2010; Wollin, Pizzari, Spagnolo, Welvaert, & Thorborg, 2018a). Two recent systematic reviews identified that athletes who possessed low hip adduction strength (as an isolated measure as well as relative to abduction strength) were more likely to suffer from hip and groin pain, with reports of four times greater risk (Ryan, DeBurca, & Mc Creesh, 2014; Whittaker et al., 2015). A recent study has also demonstrated that male soccer athletes who have had past-season groin pain for more than 6 weeks are likely to commence the next season with an increased risk of groin injury, due to lower hip adduction squeeze test strength (Esteve et al., 2018). This highlights the need for early diagnosis and comprehensive rehabilitation.

In-season monitoring of hip muscle strength can detect early groin problems in the both elite Australian Rules Football (AFL) (Crow et al., 2010) and elite football (soccer) (Wollin et al., 2018b) and can be used to evaluate recovery following match-play (Wollin et al., 2018b). Early detection of strength reductions allows prompt clinical evaluation and commencement of appropriate intervention as required (Thorborg et al., 2018). As part of a clinical reasoning process, improving strength scores may help indicate when an athlete is ready for increased resistance in exercises, progression of exercise type or complexity, and ultimately capable of higher workloads.

Of the methods available for the assessment of hip strength, the most cost-effective and commonly used method is a sphygmomanometer (Toohey, de Noronha, Taylor, & Thomas, 2018). It has been shown to be both valid and reliable for hip adduction strength testing (Delahunt, McEntee, Kennelly, Green, & Coughlan, 2011), but is susceptible to ceiling effects when testing stronger individuals (Toohey et al., 2018) and is limited to measurement of hip adductor strength only. More recently, hand-held dynamometry (HHD) has been identified as a reliable method for assessing hip strength (Kemp, Schache, Makdissi, Sims, & Crossley, 2013) and provides important information about potential groin problems and injury risk (Esteve et al., 2018; Thorborg et al., 2018; Wollin et al., 2018a, 2018b). However, HHD is susceptible to between-tester bias, with the strength and experience of the assessor influencing testing scores (Kemp et al., 2013; Thorborg, Bandholm, Schick, Jensen, & Holmich, 2013). Isokinetic dynamometry overcomes this limitation by removing the influence of assessor strength, but is costly, time-consuming, and requires considerable expertise to operate, which may preclude its use in a practical field-based setting. Recently, a novel field-testing device (The GroinBar, VALD Performance, Australia) has been developed to assess hip strength of both limbs simultaneously. It comprises an adjustable rig fitted with four independent and adjustable custom-made uniaxial load cells. Like isokinetic dynamometry, the impact of examiner strength is eliminated, however, the device is portable and does not require extensive training or expertise for use. The device has been shown to have excellent test re-test reliability for adductor strength testing (ICC = 0.94) (Ryan, Kempton, Pacecca, & Coutts, 2018), although normative values in elite athletes are yet to be established, and it is not known if strength scores are related to scores measured with the commonly used HHD.

The primary aim of this study was to assess concurrent validity of the new, novel externally–fixed dynamometer (GroinBar) with HHD. The second aim was to provide normative GroinBar scores for elite AFL and football (soccer) players. Our final aim was to evaluate preliminary predictive validity of the GroinBar and HHD in this population by comparing strength results with patient reported outcome scores and groin pain history. Our hypotheses were that the GroinBar and HHD would be moderately correlated, and that we would find an association between strength measurements and injury history or self-reported outcomes.

Section snippets

Methods

This study was conducted from June to July 2017. Players from two AFL clubs and one A-League football club (senior and youth team) were invited to participate. All participants were male. Players were eligible to participate if they were present and available at the club at the time of testing. Those who were unable to participate in full training because of an injury, sickness or any physical complaint were excluded. Height, weight and leg length were measured by a single investigator (MO) and

Data analysis

Force data from The GroinBar were transferred to a personal computer at 50 Hz through a USB connection using custom made software (Scoreboard, VALD Performance, Australia). The peak force for both limbs (dominant and non-dominant) for each position (short or long lever) was determined automatically through the Scoreboard software and expressed as absolute (N) and relative values (N/kg). Peak adductor and abductor torque was calculated using weight and limb length for the long lever test

Results

In total, 67 male athletes including 36 AFL players and 31 football (soccer) players were recruited for this study (age = 20.1 ± 3.40, height = 1.84 m ± 0.08, body mass = 79.2 kg ± 9.19, BMI = 23.4 ± 1.80). (Table 1).

Moderate to good correlations (0.53–0.71) were identified between the GroinBar and HHD strength tests for hip adduction and abduction in the long lever position (Table 2). Adduction scores showed higher correlations compared with abduction scores, and the ratios displayed only a

Discussion

This study identified moderate to good association between the GroinBar device and HHD, which is the current best practice for clinically assessing hip and groin strength (Kemp et al., 2013; Thorborg et al., 2018). Preliminary concurrent validity of the GroinBar was demonstrated since findings were equivalent to HHD when evaluating strength results between players with groin problems and those without. Neither strength testing methods identified strength deficits in those with groin problems or

Limitations

No adverse events or injuries occurred during the testing. There were several limitations to this study that warrant discussion. First, the sample size may not have been large enough to detect small to moderate associations between strength and injury history or HAGOS subscale scores. Also, with numerous maximal efforts needing to be performed, there is some potential for fatigue to affect the latter tests. Randomisation was utilised to reduce this factor, however, it is still a possibility

Clinical implications

This study identified a moderate to good correlation between the GroinBar and HHD for hip adduction and abduction strength testing. Given its external fixation and ability to quickly obtain unilateral strength results, the GroinBar may be a useful tool in busy sporting and clinic environments. We found no association between HAGOS subscale scores and isometric strength measurement in elite AFL and soccer players. Normative strength values for male AFL and football (soccer) players have been

Conflicts of interest-

None.

Ethical statements

This project was approved by the La Trobe University Human Ethics Committee (HEC 16–118).

Funding

N/A.

Acknowledgements

N/A.

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