[Purpose] The purpose of this study was to propose a table height that can reduce shoulder muscle fatigue by analyzing and comparing median frequencies of shoulder muscles at different table heights when performing therapeutic ultrasounds work. [Subjects and Methods] The subjects were 63 healthy male adults who were equally and randomly assigned to a standard height group (SHG), a high height group (HHG), and a low height group (LHG). The standard table height was set at the level of the elbow joint when the subjects flexed their elbow while in a sitting position. High height and low height were set 10 cm higher and 10 cm lower, respectively, than the standard height. Muscle fatigue of the upper trapezius, middle deltoid, rhomboid, and infraspinatus of the subjects was measured during ultrasound treatment work at each table height. [Results] Median frequencies of the upper trapezius, middle deltoid, rhomboid, and infraspinatus muscles were significantly lower in the HHG than in to the LHG. [Conclusion] When therapeutic ultrasound is performed using a table that has a height lower than that of the elbow joint, the median frequency of the shoulder muscle increases, hence decreasing muscle fatigue. This way, musculoskeletal pain as a result of performing therapeutic ultrasound can be prevented.

[Purpose] The purpose of this study was to analyze changes in the electromyographic activities of the lumbar erector spinae caused by inversion traction in order to verify the relaxation effect. [Subjects and Methods] The subjects included 60 healthy male adults who were equally and randomly assigned to a 30–30° group, a 30–60° group, and a 60–60° group. Inversion traction was performed for six minutes, and the electromyographic activities of the lumbar erector spinae (L2, L4) were measured before and after inversion traction. [Results] The root mean square values at the L2 and L4 levels on both sides were statistically significantly higher after inversion traction compared with before inversion traction. Before inversion traction, the root mean square values at the L2 and L4 levels on both sides in the 30–60° group and 60–60° group were significantly higher than those in the 30–30° group, while the root mean square values at the L2 and L4 levels on both sides showed no significant differences between the groups before inversion traction. [Conclusion] The findings of this study indicated that IT is more likely to elicits an increase in muscle tension and prevent relaxation of the lumbar erector spinae.

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