Be the low—intensity muscle contractions can be evaluated by measuring muscle bundle length, using an ultrasonic measuring device?

Abstract

Objective: When performing rehabilitation for post-orthopedic patients, it is necessary to evaluate and treat abnormal muscle tone. In recent years, ultrasonic measuring devices have often been used for simple evaluations of skeletal muscles and soft tissues in clinical practice, and they have been suggested for muscle activity measurement. The objective of this study was to clarify whether the low-intensity muscle contractions can be evaluated by measuring muscle bundle length, using an ultrasonic measuring device.

Method: The subjects were nine healthy people and 16 limbs. The task was an isometric knee extension of 30% or less of the maximum voluntary contraction. Using a surface electromyogram and an ultrasonic measuring device, the relative values of the EMG integrated value and of the amount of change in muscle bundle length were measured. The relationship between muscle bundle length and muscle activity was determined using curve regression analysis.

Results: The result of the curve regression analysis was r² = 0.736 (p < 0.001), and it strongly suggested that the relative value of the muscle bundle length increased, while the relative value of the EMG integral value increased.

Conclusion: It was suggested that the ultrasonic measurement of the muscle bundle length could be used to evaluate low-intensity muscle contractions for the vastus lateralis.