2014 Volume 31 Issue 1 Pages 7-12
Since shoulder stiffness is characterized by subjective symptoms centered mainly around the trapezius muscle, an objective evaluation may aid in understanding this condition. Thus, assessing the distribution and intensity of muscle activity may help to characterize shoulder stiffness. Using myogenic potential topography, the present study aimed to identify the changes in the state of the trapezius muscle among subjects with shoulder stiffness. Surface electromyogram recordings were obtained from the trapezius region of eight healthy women immediately before exercise, immediately after the end of exercise, and at the end of a 20-min convalescence period. Surface electromyogram data were analyzed by fast Fourier transform (FFT) , and power spectra were obtained. Based on the analyzed data, myogenic potential topography was composed at 6-bit resolution. Women who complained of shoulder stiffness showed remarkable changes in the low-frequency domain of the surface electromyogram immediately after the end of exercise. Further, these changes were in accordance with the positions of the subjective symptoms reported by the subjects. Therefore, these events suggest a phenomenon specific to shoulder stiffness. Visually identifying the physiological alteration of muscle activity is possible using myogenic potential topography.