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July 2013

Interrater reliability of muscle tone, stiffness and elasticity measurements of rectus femoris and bicepsbrachii in healthy young and older males

S. Agyapong-Badu, L. Aird, L. Bailey, K. Mooney, J. Mullix, M. Warner, D. Samuel, M. Stokes
Faculty of Health Sciences, University of Southampton, United Kingdom
Working Papers in Health Sciences (Summer 2013, ISSN 2051-6266 / 20130021)

Purpose
To examine interrater and within-session reliability of using the MyotonPRO device for measuring non-neural tone and mechanical properties of the rectus femoris and biceps brachii muscles in healthy young and older adults.

Methods
Forty-two healthy males were studied: n=21 aged 25.9 (SD 4.4) years and n=21 aged 72.1 (SD 4.9) years. The MyotonPRO device applied brief, low force mechanical impulses to the muscle belly to produce damped oscillations of the muscle at rest. Computing of the parameters was made automatically from the oscillation curve of non-neural mechanical tone (state of intrinsic tension) measured as frequency [Hz], dynamic stiffness [N/m] and elasticity (logarithmic decrement).

Analysis
The means and standard deviations of all three parameters for each rater were calculated. Reliability was assessed using intra-class correlation coefficients (ICCs) and Bland and Altman analysis.

Results
Excellent within-session intra-rater reliability was demonstrated by raters for both participant groups (intraclass
correlation coefficients, ICC 3,2 = 0.94-0.99). Interrater reliability was excellent for all rectus femoris parameters in the young (ICC 3,1= 0.92-0.95) and older group (0.86-0.94). In biceps brachii, reliability was excellent in the young group (0.78-0.94) and for elasticity in the older group (0.89) but was only classed as good for tone (0.67) and stiffness (0.68).

Different raters obtained acceptably similar results for all three parameters of rectus femoris in both age groups and for biceps brachii in the young group, and for elasticity only in the older group. The findings indicate that the MyotonPRO
has potential use for objective assessment of mechanical muscle properties in clinical and research settings and that the protocol for locating the site for testing biceps brachii in older participants could be modified to improve reliability.

Implications: The MyotonPRO device can be used reliably by different users to assess muscle parameters in healthy people of different ages. Further studies are needed to add to the existing literature to establish Myoton technology as a valid and reliable clinical and research tool for examining the effects of injury, disease and interventions in various muscles in clinical conditions.

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