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March 2012

Reliability, Validity, and Responsiveness of Myotonometric Measurement of Muscle Tone, Elasticity, and Stiffness in Patients With Stroke

L. Chuang, C. Wu, K. Lin
School of Occupational Therapy, College of Medicine, National Taiwan University; Division of Occupational Therapy, Department of Physical Medicine and Rehabilitation, National Taiwan University Hospital
American Congress of Rehabilitation Medicine (2012) (DOI: 10.1016/j.apmr.2011.09.014)

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.

Findings from this study indicate that the Myoton-3 myometer can be applied as a reliable, valid, and responsive device
for objectively quantifying muscle tone, elasticity, and stiffness of resting forearm muscles in patients with stroke. Mechanical characterization of the skeletal muscle measured by the Myoton-3 myometer may provide new insights into muscle functions to diagnose and treat muscle pathophysiology. Thus, performance documented by the Myoton-3 might be a useful indicator of biomechanical tissue changes in clinical practice and research. Further research is needed to study the clinical utility of the instrument based on a larger sample.

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