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Practical implications

• Inter-observer reliability of MyotonPRO ranged from good to excellent.
• Inter-day reliability of MyotonPRO ranged from good to excellent.
• Coefficient of variation values were in a range from 3.9–11.0%.
• MyotonPRO is a repeatable tool to quantify muscle mechanical properties.

The purpose of the present study was to investigate the inter-rater and intra-rater reliability of the MyotonPRO for measuring the mechanical properties of the upper limb muscles in patients with chronic stroke. The study was conducted with 20 stroke patients (14 males, 6 females) with age range of 36–84 years (65.1 ± 11.2 years). The oscillation frequency, stiffness, and logarithmic decrement of the biceps brachii, triceps brachii, deltoid, and upper trapezius muscles were measured using a MyotonPRO (Myoton AS, Tallinn, Estonia).

The measurements were conducted by two physiotherapists to determine the inter-rater reliability of the device. A physiotherapist repeated the measurements 3 days after the first measurements for determining the intra-rater reliability of the device. The ICCs of all assessed muscles ranged between 0.72 and 0.97. The coefficient of variation of all muscles ranged within 3.2%-11.0%, from 3.4–9.7% for oscillation frequency, from 3.9–7.4% for stiffness, and from 3.2–11.0% for decrement. The standard error of measurement in the assessed muscles ranged from 0.5 to 1.2 Hz for frequency, from 9.2 to 21.2 N/m for stiffness, and from 0.1 to 0.4 for decrement.

The results obtained show that MyotonPRO has a good to excellent intra-rater and inter-rater reliability for measuring the tone, stiffness, and elasticity of the deltoid, biceps brachii, triceps brachii, and upper trapezius muscles in patients with chronic stroke. MyotonPRO can be used for the diagnostic and therapeutic intention in patients with chronic stroke.

Keywords: myotonometry, reliability, stroke, muscle, stiffness, tone, elasticity

The results obtained show that the MyotonPRO has a good to excellent intra-rater and inter-rater reliability for measuring the tone, stiffness, and elasticity of the deltoid, biceps brachii, triceps brachii, and upper trapezius muscles in patients with chronic stroke. The findings demonstrated that the MyotonPRO is a reliable and repeatable tool for quantifying the muscle mechanical properties in stroke patients. The MyotonPRO can be used for diagnostic and therapeutic intentions.