What is the relationship among repeated heel raises, plantarflexor peak force, and functional performance in people with muscle disease?



Document Type


Conference Title/Conference Publication

15th International World Congress of Physical Therapy Meeting


World Confederation for Physical Therapy


Vancouver, Canada

Conference Dates

June 2, 2007-June 6, 2007

Date of Presentation



PURPOSE: Manual muscle testing (MMT) is an ineffectual method of plantarflexor (PF) strength assessment. Repeated heel raises has been proposed as a method of PF strength testing that circumvents the limitations of the MMT. The purpose of this study was to examine the relationship among heel raises, PF peak force, and functional performance in subjects with inflammatory muscle disease (myositis). RELEVANCE: It is unclear if repeated heel raises reflect peak muscle force or other aspects of PF muscle performance. PARTICIPANTS: Forty-three subjects with myositis obtained through a sample of convenience at a Federal hospital participated in the study (age 66.0 ±7.5 years, 13 females). METHODS: This was a prospective, observational, clinical trial with a between-groups design. Group assignment was based on the ability to complete a single heel raise (Able, n=21; Unable, n=22). Repeated, single-limb heel raises were performed using a wedge (20 degrees), metronome (60 bpm) to standardize repetition speed, and upper extremity support for balance. The isometric peak force (10 bilateral muscle groups) was obtained with a fixed-dynamometer using a force transducer and scaled to body weight. Functional performance was represented by self-selected gait speed (in statures) obtained with foot switches over a 10 m distance and summed timed tests of function (rolling, supine-to-sit, and sit-to-stand). ANALYSIS: Analysis of difference was determined by the Kruskal-Wallis test and analysis of relationships were determined using the Spearman’s rho (ρ; α = 0.05). RESULTS: The ability to complete a single heel raise resulted in significant group differences in PF peak force, summed total peak force, timed tests of function, and gait speed (p ≤ 0.008). Repeated heel raises for all subjects were significantly correlated with PF peak force (ρ = 0.59, p < 0.001), summed total peak force (ρ = 0.51, p = 0.001), timed tests of function (ρ = −0.36, p = 0.02) and gait speed (ρ = 0.63; p < 0.001). However, 22 subjects were unable to complete a single heel raise. With the exception of gait speed (ρ = 0.56, p = 0.008), all of the aforementioned correlations were not significant when subjects unable to complete the heel raise task were excluded from the analysis. CONCLUSIONS: There are significant differences in muscle strength and functional performance between people with myositis who can and cannot perform the single-limb heel raise task. The repeated heel raise is an important functional task that is associated with gait speed across all subjects. However, the repeated heel raise test demonstrated a significant floor effect in this study, as 51% of the subjects were unable to perform the task. When the subjects were able to complete one or more heel raises, the number of heel raises completed were not correlated with PF strength. IMPLICATIONS: The ability to perform a single heel raise provides important clinical distinctions between subjects with muscle disease. In those able to perform the task, repeated heel raises are associated with gait performance. However, repetitions of heel raises cannot be used as a proxy for PF strength in this patient population. KEYWORDS: strength, assessment, function, muscle disease. FUNDING ACKNOWLEDGEMENTS: National Institute of Neurological Disorders and Stroke, IRP 02-N-0121.

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