Deformation of Skin in 4D Scans as an Indicator of Muscular Activity Compared to EMG in Biceps Contraction

EMG is the standard technique to measure muscle activity, but it has important disadvantages, such as the need of invasive instrumentation. 4D scanning allows measuring body shape deformation during motion, as an indirect measure of muscle activity. We compared EMG and skin deformation in 8 participants who were measured with a 4D scanner (Move4D) and EMG sensors, performing isometric biceps contraction. EMG and deformation were compared in terms of increase and decrease rates during contraction and relaxation, and range of variation of peak values. Results show no differences during contraction and differences during muscle relaxation, and that peak values in deformation were more similar across repetitions than EMG. This shows that shape deformation can be used as an indirect indicator of muscular activity.