Long-term phase angle muscle imaging under electrical muscle stimulation (EMS) by phase angle electrical impedance tomography.

ABSTRACT

Phase angle muscle imaging has been proposed by phase angle electrical impedance tomography under EMS for long-term monitoring of muscle quality improvement, especially focusing on calf muscles. In the experiments, twenty-four subjects are randomly assigned either to three groups control group (CG, n = 8), low voltage intensity of EMS training group (LG, n = 8), and optimal voltage intensity of EMS training group (OG, n = 8). From the experimental results, phase angle distribution images Ф are cleared reconstructed by ФEIT as four muscle compartments over five weeks experiments, which are called the M1 composed of gastrocnemius, M2 composed of soleus, M3 composed of tibialis-posterior, flexor digitorum longus, and flexor pollicis longus, and M4 composed of the tibialis anterior, extensor digitorum longus, and peroneus longus. Ф is inversely correlated with age, namely the Ф decreases with increasing age. A paired samples t-test was conducted to elucidate the statistical significance of spatial-mean phase angle in all domain <Ф>Ω and in each muscle compartment <Ф>M with reference to the conventional phase angle Ф by bioelectrical impedance analysis, muscle grey-scale Gmuscle by ultrasound, and maximal dynamic strength SMax by one-repetition maximum test. From the t-test results, <Ф>Ω have good correlation with Ф and SMax. In the OG, <ФW5>Ω, ФW5, and (SMax)W5 were significantly higher than in the first week (n = 8, p < 0.05). A significant increase in the phase angle of both M1 and M4 muscle compartments is observed after five weeks in LG and OG groups. Only the OG group shows a significant increase in the phase angle of M2 after five weeks. However, no significant changes in the spatial-mean phase angle of M3 are observed in each group. In conclusion, ФEIT satisfactorily monitors the response of each compartment in calf muscle to long-term EMS training.