Sometimes, when improving the range of motion or muscle strength of the shoulder joint, we fail to obtain sufficient therapeutic effects in subjects who have difficulty in raising their arms up along the spine from a position in which the arms are at the back (belt-tying movement). In many such cases, scapular motion is inadequate or different from the normal motion during belt-tying movement. On the other hand, we have experienced several cases in which the scapula moved more smoothly and belt-tying movement was improved by strengthening the scapular muscles using exercise therapy. This study aimed to elucidate the muscle activity pattern of scapular muscles during the belt-tying movement. We found that the upper trapezius muscle fibers elevate the scapula and middle trapezius muscle fibers maintain scapula adduction; and the lower trapezius muscle fibers and the serratus anterior muscle were considered to regulate anterior inclination of the scapula at T12 and lower vertebrae. Patients experiencing difficulty in belt-tying movement should receive a quantitative and qualitative assessment of the timing of movement of the trapezius muscle fibers and the serratus anterior muscle after gaining an understanding of the stage in which the patient starts to feel difficulty in movement.
