Characterizing skin surface variations during motions to improve the design of sEMG monitoring upper-body training garments

<i>Objectives.</i> This study aimed to characterize skin surface variations during motion to improve the design of surface electromyography (sEMG) monitoring upper-body training garments. <i>Methods.</i> A combination of the surface tracing method and the body scanning method was employed to measure the skin surface variations on the upper body during 11 dynamic poses, including length changes in both horizontal and longitudinal directions, assessment of area changes within specific subdivisions, and the amplitude of skin strain on the main muscle regions. <i>Results.</i> The mean skin deformation of the participants was analyzed across the different postures. The longitudinal strain at the most protruding part of the elbow exceeds 30% during elbow joint motions, the transverse line at the sleeve cap exhibits a strain of more than 40% and the longitudinal lines under the armpit reach a strain of 80% during shoulder joint motions. Transverse dimensions on the lateral body are always under tension with a maximum strain approaching 20%, while longitudinal dimensions exhibit a strain of more than 50% during lumbar motions. <i>Conclusions.</i> The results indicate an integrated overall design for sEMG monitoring upper-body training garments, including the design of the suit's style, pattern, laminated fabric electrodes and wire layout.