Designing and implementing testing and monitoring procedures to identify athletes who are at increased risk for suffering hip-related pathology is crucial for sustained, high-level, ice hockey performance.
First, understanding the relationship between of multiplanar hip strength, motion, and how they operate in more complex, functional tasks, are of paramount importance for identifying athletes who are “at risk” of sustaining a new non-contact injury. A recent extensive review of the research regarding testing and management of athletes with groin pain was done by Thorborg and colleagues (2018), if interested . Although beyond the scope of this article, it’s important to note that imaging plays a role in detecting serious pathology in athletes presenting with pain or dysfunction and may, in some cases, also serve to give more credence to the diagnostic work-up process if it matches clinical signs and symptoms . I will focus on physical screening and monitoring strategies for determination of at-risk athletes, in effort to prevent and/or alleviate common hip-related pathology.
Part 1: How non-contact injuries occur in sport and why well-functioning hips are necessary for elite ice hockey performance.
Part 2: Prevalence of hip injures in ice hockey, how and to whom they occur, with a special focus on groin strains.
Part 3: Review of where groin pain may actually be coming from (spoiler alert: it may not be from the groin muscles)
Part 4: The financial cost of injury for NHL players, and the potential costs to sustained high-level performance and long-term health.
I strongly advise taking the time to go through each of these articles, at some point. I intentionally broke up this article series into many parts to make the content of each article more easily digestible.
The FMS and Injury Prediction
Pre-participation screening exams have been developed in an effort to identify athletes who may be at increased risk for sustaining subsequent injuries. Despite the Functional Movement Screen (FMS) being the most prevalent standardized screening tool available, it has been consistently shown to be a poor predictor of injury risk in athletes [2-4]. Although its intra-rater reliability (degree of agreement among repeated test administrations) and inter-rater reliability (degree of agreement between different practitioners conducting the test) are generally quite good [5-7], the prognostic accuracy of the FMS was only slightly better than flipping a coin for correctly classifying Division II athletes most at risk for subsequent injury . In this study, the FMS composite score was used to predict injury risk. This is the most commonly evaluated FMS metric, and it appears to lack injury predictability. When using the FMS as a tool to identify at-risk athletes, research suggests that it may be wise to focus on asymmetry identified in one or more of the FMS tests to help pinpoint athletes that have increased injury susceptibility [8, 9], as opposed to concentrating on the FMS composite score.
Specific to ice hockey, the FMS has failed to show adequate clinical utility to identify those at risk for injury in youth , male NCAA Division I , men’s junior [11, 12], or East Coast Hockey League (ECHL) players . Although the FMS may be a valuable tool for practitioners in a variety of contexts, current data suggests that it has limited, if any, capacity for injury risk identification in ice hockey athletes. Through this analysis, I’m not trying to discredit the FMS; it certainly has value in many different settings. For example, as I noted above, it’s a great standardized tool for evaluating asymmetry, which may help identify at-risk athletes. However, I would choose a more time-efficient protocol that may have better translation to ice hockey athletes.
The SEBT and Y-Balance Test
The Star Excursion Balance Test (SEBT) is a reliable measure and a valid dynamic test to predict risk of lower extremity injury, to identify dynamic balance deficits in patients with lower extremity conditions, and to be responsive to training programs in healthy participants and those with lower extremity conditions . The SEBT is a series of single-limb squats using the nonstance limb to reach maximally to touch a point on the ground, and includes 8 reaching directions . The Y-Balance is essentially a modified (i.e. condensed) version of the SEBT, using 3 reaching directions instead of 8 . Although very similar tests, it’s important to note that there appear to be slightly different outcomes between the two when reaching in the forward direction [17, 18]. Therefore, using data from one test to insinuate performance on the other is not an advisable approach. Here are images of the 3 Y-Balance Test reaching directions, A) Anterior, B) Posteromedial, and C) Posterolateral:
There’s conflicting evidence as to whether athletes with groin pain have ROM impairments, compared with controls [19-23], but evaluating hip ROM may be able to distinguish those with femoroacetabular impingement (FAI) from those without . Performance on the Y-Balance Test has been associated with hip flexion ROM , hip extension strength and hip internal rotation ROM , lower body flexibility asymmetry , hip abduction function and strength [28, 29], risk factors for ACL tears  and readiness to return to sport after ACL surgery , and lower body injury risk [31-42]. A recent meta-analysis determined that a composite reach score difference of less than 94% of limb length and an anterior reach difference of 4 cm or greater between limbs may be predictors for increased injury risk in athletes . There is also research conducted in large athletic cohorts that found no correlation between Y-Balance Test performance and injury risk [43, 44]. It’s clear that sport injuries are multifactorial; using a single test alone, such as the Y-Balance, to screen for injury risk in athletes, is not an advisable approach.
I believe that integration of a standardized screening regime requiring single-leg balance, multi-joint coordination, motor control, ROM, and a minor degree of lower body strength, is a time-efficient way to evaluate multiple athletic components and asymmetries in ice hockey athletes (and other athletes who spend most of their time on a single leg). The Y-Balance Test (or SEBT) is an example of one of these multifaceted tests, and there’s a significant body of research supporting its use for identifying, or at least aiding in the identification of athletes at increased risk for injury.
Manual Muscle Testing to Assess Hip Strength
In Part 1, I discussed the unique contribution of hip musculature for producing on-ice locomotion, including on-ice acceleration and sprinting prowess [45-51]. In Part 2, we discovered how lack of absolute hip adduction strength and/or lack of hip adduction relative to hip abduction strength, may increase risk for sustaining a groin injury [19, 52-58]. In addition to the hips, the importance of the abdominal muscles cannot be overstated. The integration of the hip and abdominal muscles plays a significant role in appropriate pelvic positioning during various intricate skating movements, as well as successful performance in explosive rotational movements integral to ice hockey, such as shooting, passing, and quick turning ; this concept is discussed in greater detail in Part 3.
The importance of collecting objective hip strength measurements is obvious to many. Manual muscle testing (MMT) is often used for this collection . Although no equipment aside from a hand-held dynamometer is necessary, the way that hip strength is tested using this simple device must be considered. An isometric squeeze test can be done, but this is typically performed bilaterally. There appear to be differences in force-generating capabilities between bilateral and unilateral movements [61-63], which could potentially impact the results.
The hand-held dynamometer, itself, has been used since the 1940’s  and is a reliable tool for assessing hip muscle strength . However, standardization of the protocol is of paramount importance to ensure consistent measurement criteria. I can’t stress this point enough. Lack of standardization can result in data misrepresentation in a variety of ways, including through strength/style differences among practitioners and variance in athlete testing positions. For example, Thorborg et al. (2013) found that female testers consistently produced lower values compared with their male tester counterparts . This suggests that the values recorded using hand-held dynamometry depend on the resistance offered by the assessor. Light et al. (2016) found differences in hip strength values between long-lever (i.e. when measured from the ankle) and short-lever (i.e. when measured from below the knee) positions . Measuring an athlete at different anatomical points will undoubtedly misrepresent changes in their hip strength. Here is an image of manual muscle testing (MMT) of side-lying hip adduction via Harøy et al. (2017), :
Hand-held dynamometers have been used to assess eccentric strength (“break testing”) and isometric testing (“make testing”). High correlations generally exist between the two methods [68, 69], but strength values are typically higher during break (eccentric strength) testing [68, 70]. Break (eccentric strength) testing may be the superior method when it comes to groin pain identification . However, make (isometric strength) testing has advantages of (1) being more reliable  and (2) producing less stress on the musculoskeletal system, which could minimize testing-induced injury risk and delayed onset muscle soreness from the testing [55, 72]. Additionally, resistance placed at long-lever positions (i.e. by the ankles) appears to be a better predictor of previous groin pathology, compared with resistance placed at short-lever positions (i.e. slightly below the knees) during testing [66, 73, 74]. Above all else, the standardization of measurement protocols is of utmost importance. Hébert and colleagues suggest that the following aspects of protocol administration should be strongly considered :
- The same tester should be used for all measurements, if possible.
- The participants should be stabilized while measuring muscle strength.
- Hip flexion should be measured in the standing or supine position.
- Hip extension is best measured in the standing or prone standing positions; the prone position is not recommended.
- Internal and external rotation are more reliably measured in hip flexion
I’ve come up with a few suggestions based on the literature reviewed on hip strength testing. First and foremost, I advise using a device that provides objective data and a standardized procedure for data collection to minimize measurement error and promote reliable, longitudinal results. Using dynamometry or a sphygmomanometer are both great options. However, a new device by Vald Performance, the GroinBar, has recently shown greater measurement precision than either of these two methods . The GroinBar is far more expensive than the former two methods, but is a very high-quality product and has the benefit of not being dependent on practitioner skill/strength. You can learn more above the GroinBar here. Please note that I’m not affiliated with this company or device in any way.
Here are my thoughts on specific positions for hip strength testing:
- Unilateral 90-degree (short-lever) supine hip flexion*
- Unilateral 0-degree (long-lever) supine hip adduction*
- Unilateral 0-degree (long-lever) supine hip abduction*
- Unilateral 90-degree (short-lever) supine hip internal rotation
- Unilateral 90-degree (short-lever) supine hip external rotation
- Unilateral 0-degree (long-lever) prone hip extension
- Metrics of primary interest, given the current body of research
An applicable screening tool that provides objective data should be used in conjunction with a standardized procedure that is sensitive enough to identify athletes who are “at risk” of sustaining a new non-contact injury. Evaluating hip movement and strength capabilities are of principal importance for identification of these athletes, particularly in the sport of ice hockey. There are a multitude of testing/screening methods out there; the ideal method for you will depend on many factors, including available resources, budget, time, and athlete cohort. In the next article (Part 6), I’ll review the research on how to treat different types of hip pain and briefly discuss the potential impact of early sport specialization on FAI risk in ice hockey athletes.
UPDATE: Part 6 has been released and can be viewed here.
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