Evaluation of the effectiveness of electrical muscle stimulation (EMS) on human calf muscles via frequency difference electrical impedance tomography (fd-EIT).

OBJECTIVES The human skeletal muscle responds immediately under electrical muscle stimulation (EMS), and there be an immediate physiological response in human skeletal muscle. Response muscle areas of human calf muscles under electrical muscle stimulation (EMS) have been detected by frequency difference electrical impedance tomography (fd-EIT). APPROACH The experimental protocol consists of four parts: pre-training (pre), training (tra), post-training (post), and relaxation (relax) parts. The relaxation part has three types of relaxation conditions which are massage relaxation (MR), cold pack relaxation (CR) and hot pack relaxation (HR). MAIN RESULTS From the experimental results, conductivity distribution images σp (p means protocol = pre, tra, post, or relax) are clearly reconstructed by fd-EIT as response muscle areas, which are called M1 response area composed of gastrocnemius muscle and M2 response area composed of tibialis anterior muscle, extensor digitorum longus muscle, and peroneus longus muscle. Paired samples t-test was conducted to elucidate the statistical significance of spatial-mean conductivities M1 and M2 in M1 and M2 with reference of conventional extracellular water ratio ꞵp by bioelectrical impedance analysis (BIA). SIGNIFICANCE From the t-test results, M1 and M2 have good correlations with ꞵp. In the post-training part, the and ꞵpost were significantly higher than those in the pre-training part (n = 24, p and the relax-pre difference ratios of extracellular water ratio Δꞵrelax-pre in both MR and CR were lower; on the contrary, the Δ and Δꞵrelax-pre in HR were significantly higher than those in post-pre difference ratios of spatial-mean conductivity Δ (n = 8, p M1 and M2 is caused by the changes in muscle extracellular volumes. In conclusion, fd-EIT satisfactorily evaluates the effectiveness of human calf muscles under EMS.