Reliability, validity, and responsiveness of myotonometric measurement of muscle tone, elasticity, and stiffness in patients with stroke

Objective: To assess the metric properties of a myotonometer. Design: Metric study. Setting: Three medical centers. Participants: Stroke patients (N=67). Intervention: Upper-extremity rehabilitation programs. Main Outcome Measures: The tone, elasticity, and stiffness of relaxed extensor digitorum, flexor carpi radialis, and flexor carpi ulnaris were measured using the myotonometer. Fifty-eight patients completed the myotonometer measures twice at pretreatment. The myotonometric measurement and the criteria measures, including hand strength (grip, lateral pinch, and palmar pinch strength) and Action Research Arm Test (ARAT) were administered at pretreatment and posttreatment. Results: The myotonometer showed high test-retest reliability for muscle properties in 3 muscles. Significant correlations existed between the tone and stiffness of the 3 muscles and palmar pinch strength, between those of the flexor carpi muscles and lateral pinch strength, and between those of the flexor carpi radialis and the ARAT at posttreatment. The posttreatment elasticity of the 2 flexor carpi muscles was significantly correlated with grip strength. The pretreatment elasticity of the flexor carpi ulnaris was significantly correlated with posttreatment grip strength, and the pretreatment muscle tone and stiffness of the flexor carpi radialis were significantly correlated with palmar pinch strength and the ARAT. The responsiveness of the extensor digitorum was higher than that of the flexor carpi radialis and ulnaris. Muscle stiffness was more responsive than tone and elasticity in 3 muscles. Conclusions: Myotonometry can be a reliable, valid, and responsive outcome measure for assessing muscle properties after stroke rehabilitation.