Quadriceps muscle tone, elasticity and stiffness in older males: reliability and symmetry using the MyotonPRO.

BACKGROUND The MyotonPRO (Myoton Ltd; London) is a new portable device for measuring muscle mechanical properties (e.g. tone) and its reliability has yet to be established. Little is known about between-limb symmetry of mechanical properties in healthy older people, despite symmetry often being used as a measure of unilateral abnormalities in clinical assessment. Since quadriceps is important for mobility, it was selected for the present study. AIMS To investigate: (i) between-day intra-rater reliability of a novice user of MyotonPRO; (ii) between-side symmetry of mechanical properties of quadriceps in older males. METHODS Twenty healthy, community dwelling, right-lower-limb-dominant males (mean age 71.7, range 65-82 years) were studied. With the participant in relaxed supine lying, the MyotonPRO applied two consecutive sets of 10 taps to induce muscle oscillations of rectus femoris, from which measurements of decrement (elasticity), frequency (tone), and stiffness were obtained. Tests were performed on two occasions at the same time and day of the week, one week apart. RESULTS Repeated measurements had very high within-day (intraclass correlation coefficient, ICC 3,1>0.90) and high between-day (ICC 3,2>0.70; mean of two measurement sets) reliability. There was no statistically significant difference between muscle mechanical properties of the dominant and non-dominant muscles (<2.5% difference; p>0.05), thereby indicating symmetry. CONCLUSIONS High intra-rater reliability was established for MyotonPRO measurements of quadriceps in healthy older males, which were symmetrical between sides. These findings indicate that larger studies are warranted to establish normal reference ranges of data with which to compare patients with muscle abnormalities.