Abstract
BackgroundDue to the specific anatomy of the subtalar joint with its oblique axis, isometric pronator and supinator strength is not well documented. The purpose of this study was to determine intra- and between-session reliability of pronator and supinator strength and lower leg muscle activity measurements during maximum voluntary isometric contractions (MVIC).MethodsPronator and supinator peak torques (PT), with and without supplementary visual muscle strength biofeedback (FB), and muscular activities of peroneus longus (PL) and tibialis anterior (TA) were assessed twice 3 days apart by the same examiner in 21 healthy young male adults (mean age: 27.6 years; SD = 3.9). Limits of agreement (LoA) and minimum detectable change (MDC) were evaluated.ResultsBy applying FB, reliability of both pronator and supinator PT was improved: LoA were reduced from 32% to 26% and from 20% to 18% and MDC from 20% to 15% and from 16% to 12% in supinator and pronator PT, respectively. Learning effects in pronator and supinator PT (p < 0.05), which were present without FB, were eliminated using FB. Except for TA during pronation, muscle activities showed low reliability indicated by LoA of 51% to 79%.ConclusionsUsing supplementary biofeedback, isometric subtalar pronator and supinator strength testing is reliable in healthy subjects. LoA of 18% and 26% have to be exceeded for pronator and supinator PT, respectively, to detect relevant effects in repeated measures.
Highlights
Due to the specific anatomy of the subtalar joint with its oblique axis, isometric pronator and supinator strength is not well documented
The reliability parameters (LoA, minimum detectable change (MDC)) are presented in Table 2 according to peak torques, peak plantar pressures and the Integrated EMG (IEMG) of tibialis anterior (TA) and peroneus longus (PL)
The participants exhibited good and acceptable reliability for pronator and supinator peak torques (PT), respectively, when strength testing was supplemented by FB
Summary
Due to the specific anatomy of the subtalar joint with its oblique axis, isometric pronator and supinator strength is not well documented. Strengthening the supinators increases the eccentric contraction capacity of the muscles of the deep posterior compartment (tibialis posterior, flexor hallucis longus and flexor digitorum longus muscles) [5]. This is potentially beneficial in the prevention of running-related overuse injuries, like exercise related lower leg pain [6,7], patellofemoral pain syndrome [8], patellar tendinopathy [9], achillodynia [10,11,12] and plantar fasciitis [13,14]. MVIC measurements are advantageous when surface electromyographic (EMG) techniques are used, because there is less displacement of muscle fibres underneath the surface electrodes compared to dynamic movements [25]
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