Elsevier

Physical Therapy in Sport

Volume 42, March 2020, Pages 100-106
Physical Therapy in Sport

Original Research
Measurement properties of hip strength measured by handheld dynamometry: Reliability and validity across the range of motion

https://doi.org/10.1016/j.ptsp.2020.01.005Get rights and content

Highlights

  • Reliability of HHD for measuring hip strength is good, with some concerns with hip IR and certain positions of extension.

  • Validity of HHD is good for abduction and some positions of hip extension; however, the validity of hip IR and ER is questionable.

  • Peak torque for abduction, IR, and ER occurs in the position of greatest muscle length. Extension peak torque occurs around 90° of hip flexion.

Abstract

Objectives

Different angles and positions may influence the reliability and validity of hip strength dynamometry. This study examined the reliability and validity of hip strength measured with belt-stabilized handheld dynamometry (HHD) compared to isokinetic dynamometry (IKD) across multiple angles.

Design

Repeated measures.

Setting

Biomechanics laboratory.

Participants

Thirty healthy participants completed 3 sessions.

Main outcome measures

Hip torque was measured for hip abduction (ABD; −10°, 0°, 20°, and 40°), internal rotation (IR; −30°, −15°, 0°, 15°, and 30°), external rotation (ER; −30°, −15°, 0°, 15°, and 30°), and extension (EXT; −10°, 0°, 30°, 60°, 90°, and 120°).

Results

ABD was reliable (no intratester reliability differences p = 0.409–0.997; ICC = 0.624–0.900) and valid (no HHD-IKD difference p = 0.270–0.946; r = 0.556–0.624) measure. IR had questionable reliability (intratester reliability differences p = 0.001–0.043; ICC = 0.682–0.879) and validity (HHD-IKD differences p < 0.001; r = 0.393–0.771). ER was reliable (no intratester reliability differences p = 0.226–0.937; ICC = 0.731–0.876) but not valid (HHD-IKD differences p < 0.001–0.003; r = 0.194–0.651). EXT showed varying levels of reliability and validity; 30° was both reliable and valid. Peak torque occurred in a lengthened position for ABD, ER, and IR, and at 90° of hip flexion for EXT.

Conclusions

HHD can be an effective tool for measuring strength under certain circumstances; however, IR/ER testing should be used with caution.

Introduction

Optimal hip muscle function is important for activities of daily living and athletic performance. The hip musculature provides stabilization between the lower extremity and pelvis, as well as being a primary contributor to propulsion (Neumann, 2010). Hip muscle weakness has been identified in a number of lower extremity injuries, including acute (Friel et al., 2006) and chronic (McCann et al., 2018) ankle sprains, patellofemoral pain (Rathleff, Rathleff, Crossley, & Barton, 2014), patellofemoral osteoarthritis (Pohl, Patel, Wiley, & Ferber, 2013), iliotibial band syndrome (Noehren, Schmitz, Hempel, Westlake, & Black, 2014), anterior cruciate ligament injury (Khayambashi, Ghoddosi, Straub, & Powers, 2016), exertional medial tibial pain (Verrelst et al., 2014), and chronic hip pain (Harris-Hayes et al., 2014). In order to accurately identify these impairments in various populations, standardized testing of hip strength is necessary.

Hip strength is often measured by belt-stabilized hand-held dynamometry (HHD). While HHD of the hip has been demonstrated to be reliable (Bazett-Jones et al., 2011, Martins et al., 2017, Thorborg et al., 2010), the validity of this method compared to a gold-standard (e.g. isokinetic dynamometry [IKD]) has received limited investigation (Martins et al., 2017). Hip extension (EXT) has been reported to be valid with moderate-very large correlations between HHD and IKD (Katoh and Uchida, 2011, Kawaguchi JB, 2010, Martins et al., 2017). Large-very large correlations have been reported for hip abduction (ABD) when comparing HHD to IKD (Aramaki et al., 2016, Katoh and Uchida, 2011, Kawaguchi JB, 2010, Martins et al., 2017). Only two studies have compared HHD to IKD for hip internal (IR) and external (ER) rotation, reporting large-very large correlations (Katoh and Uchida, 2011, Martins et al., 2017). While there are limitations to using only correlations to assess validity (Hopkins, Marshall, Batterham, & Hanin, 2009), these results generally show that HHD is a valid measure of hip strength. However, these studies have tested hip strength in a limited number of positions compared to other literature and clinical practice.

The sagittal plane position in which hip strength is tested has been reported to significantly influence the torque output (Bazett-Jones, Tylinksi, Krstic, Stromquist, & Sparks, 2017, Hoglund, Wong, & Rickards, 2014). Hip extension torque output is greater when the hip is flexed to 90° (Bazett-Jones et al., 2017). Torque output is greatest in a seated position when testing hip external rotation and internal rotation (Bazett-Jones et al., 2017; Hoglund et al., 2014). Sagittal plane position does not influence hip abduction (Bazett-Jones et al., 2017), but frontal plane position has been reported to influence torque output (Neumann, 2010). These studies hypothesize that a change in the length-tension relationship of the hip muscles due to positioning is the causal factor for these differences in testing positions (Bazett-Jones et al., 2017; Hoglund et al., 2014; Neumann, 2010).

The length-tension relationship is often investigated using strength tested across the range of motion (e.g. torque-angle relationship, torque-angle curves); however, the hip musculature has received limited study in this regard. Torque-angle curves for hip abduction have consistently demonstrated a descending (e.g. negative) linear relationship, demonstrating that as the hip becomes more abducted, hip abduction torque output decreases (Kindel and Challis, 2017, Kulig et al., 1984, Neumann et al., 1988). Less consistent findings have been reported for hip extension, with one study reporting an ascending-descending (inverted U) relationship (Jensen et al., 1971) and one study reporting a descending relationship (Kindel & Challis, 2017). Both the hip internal and external rotators have been reported to have a torque-angle relationship where torque is greatest when the hip is maximally externally and internally rotated, respectively (Jarvis, 1952, May, 1966). These studies demonstrate that the hip muscles produce their greatest forces in a lengthened position (Jarvis, 1952, Kulig et al., 1984). However, no study has confirmed these relationships for hip abduction, extension, internal and external rotation across the range of motion in one group with modern testing equipment (i.e. HHD, IKD) and methodologies.

Therefore, the aims of this study are to: 1) determine the intratester reliability of HHD, 2) determine the validity of the HHD compared to IKD, and 3) describe the torque-angle curves, for hip extension, abduction, internal and external rotation strength testing across the joint range of motion.

Section snippets

Materials and methods

This study was performed with consideration of the Guidelines for Reporting Reliability and Agreement Studies (GRRAS) (Kottner et al., 2011). Thirty healthy participants (16 females, age = 21.5 ± 2.4 yrs, mass = 76.7 ± 24.1 kg, height = 1.7 ± 0.1 m) volunteered for this cross-sectional study. Sample size was based on previous research investigating similar methods (Bazett-Jones et al., 2017; Martins et al., 2017); an apriori power analysis was not performed due to limited data across testing

Results

All tests of hip strength demonstrated fair to excellent reliability across the full range of motion (ICC = 0.620–0.900) (Table 1). Measurements with the HHD between days were significantly different for hip IR (p = 0.001–0.043).

With regard to criterion validity, hip ABD strength measured with the HHD was a valid (r = 0.56–0.62, p > 0.05) measure for all angles throughout the range of motion (Table 2). Both ER and IR showed mostly small to large relationships between the measures

Discussion

The results of this study demonstrated that hip strength testing using a belt-stabilized HHD is reliable and valid across the range of motion when testing hip ABD. Testing hip ER strength with a HHD in a seated position was reliable but not a valid method when compared to the criterion measure of IKD. Hip IR strength was not reliable nor valid. Therefore, studies which use different methodologies of hip IR/ER strength testing cannot be considered equal and comparison between these measures

Conclusions

Strength measured with an IKD is considered the criterion standard. HHD can be an effective tool for measuring strength under certain circumstances. When using a HHD to measure hip strength, practitioners should be aware that a HHD will significantly underestimate strength compared to the IKD, except in ABD and EXT near neutral. The measurement properties (i.e. reliability/validity) of ABD are acceptable across the range of motion and EXT is acceptable at 30° of hip flexion. IR and ER

Ethical approval

This study was approve by the Institutional Review Board at Carroll University.

Funding

The Carroll University Pioneer Scholar Summer Undergraduate Grant Program funded this project.

Declaration of competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgements

The Carroll University Pioneer Scholar Summer Undergraduate Grant Program funded this project. Stephanie Bandura assisted with data collection. Neal Glaviano provided a review of the manuscript.

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