Updated reliability and normative values for the standing heel-rise test in healthy adults

Abstract

Objectives

The heel-rise test is used to assess the strength and endurance of the plantar flexors in everyday clinical practice. However, several factors may affect outcomes, including sex, age, body mass index and activity level. The aims of this study were to revisit the reliability and normative values of this test, and establish normative equations accounting for several factors.

Design

Cross-sectional observational study with test–retest.

Setting

Community.

Participants

Volunteers (n = 566, age 20 to 81 years).

Interventions

Subjects performed single-legged heel rises to fatigue, standing on a 10° incline, once on each leg. A subset of subjects (n = 32) repeated the test 1 week later. Reliability was quantified using intraclass (ICC) correlation coefficients and Bland–Altman plots {mean difference [95% limits of agreement (LOA)]}, whereas the impact of sex, age, body mass index and activity level on the number of heel rises was determined using non-parametric regression models.

Results

The test showed excellent reliability (ICC = 1.0 right leg, 1.0 left leg), with mean between-day differences in the total number of heel-rise repetitions of 0.2 (95% LOA −6.2 to 6.5) and 0.1 (95% LOA −6.1 to 6.2) for right and left legs, respectively. Overall, males completed more repetitions than females (median 24 vs 21). However, older females (age >60 years) outperformed older males. According to the model, younger males with higher activity levels can complete the most heel rises.

Conclusions

The heel-rise test is highly reliable. The regression models herein can be employed by clinicians to evaluate the outcomes of heel-rise tests of individuals against a comparable normative population.

Introduction

The single-legged heel-rise test (HRT) is often used in clinical practice and research to assess the strength and endurance of the plantar flexors [1]. Among other applications, outcome scores from this test have been used to determine treatment efficacy following Achilles tendon ruptures [2] and the effects of exercise programmes on the function of elderly individuals [3]. Outcomes from this test have also been associated with survival rates in patients on renal replacement therapy [4], severity of cardiovascular disease [5] and the presence of lower-extremity musculoskeletal injuries [6]. Clearly, the HRT is a valuable tool for clinicians operating in a variety of practical settings.

Although the contralateral limb is often used as the reference for comparison of clinical scores, this does not always reflect optimal function in the presence of bilateral deficits, previous injuries or certain population groups (e.g. athletes and elderly). For these reasons, it is important to have normative values with which clinical outcome scores can be compared. In 1995, Lunsford and Perry [7] recommended that 25 repetitions should be viewed as the criterion for normal HRT performance in both males and females following the testing of 203 healthy adults (age 20 to 50 years). Although their study was considered seminal in the field, it scored poorly on a modified Downs and Black quality assessment checklist [1], and did not report the reliability of their testing procedure. Furthermore, despite investigating sex differences, Lunsford and Perry did not account for potential between-leg differences [8], [9], or the impact of age, body mass index (BMI) and activity levels on heel-rise performance [9], [10]. Indeed, previous studies have reported decreased HRT performance with increased age by 20 years [9], higher BMI [10] and participation in fewer endurance-based physical activities [11]. Furthermore, sedentary individuals exhibit lesser plantar flexor muscle strength [12] and endurance [13] capacities compared with active individuals during isokinetic dynamometry testing.

To monitor changes over time, the reproducibility of measures is vital so that changes in outcome scores reflect meaningful changes in an individual’s function (e.g. improvements in HRT scores reflect improvements in plantar flexor strength and endurance, and functional abilities of individuals). Overall, the HRT has demonstrated good to excellent reliability [intraclass correlation coefficients (ICC) 0.78 to 0.99] [14], [15], [16], [17], [18], with the standard error of measurements ranging from two to six repetitions [14], [16], [17], [18]. The difference in the reliability of the HRT across studies most likely reflects differences in testing protocols and populations investigated, highlighting the importance of documenting the reliability of specific testing protocols in research to assist readers and test users to interpret data.

The aims of this study were to revisit the reliability of the HRT, re-examine normative test scores in a large sample of healthy adults, and establish normative equations of HRT performance, while taking differences in sex, age, BMI and physical activity levels into consideration. On the basis of previous work [7], [9], [19], [20], minimal side-to-side differences were expected, with older age, female sex, higher BMI and lower activity levels expected to negatively impact HRT performance.