Hybrid Training System with Electrical Stimulation for Possible Use in the International Space Station

Abstract

The musculoskeletal system of astronauts degenerates in the International Space Station (ISS) under microgravity. There are various countermeasures to prevent this degeneration, but they often require large-scale facilities. Therefore, convenient and effective training methods to prevent degeneration are strongly desired. Our group proposed an innovative method called “hybrid training” (HT) and verified the effects of the training in healthy subjects under 1 g of Earth’s gravity and simulated microgravity. The HT combines voluntary and electrically induced muscle contractions. In clinical settings, this method could increase the effectiveness of strength training programs for the elderly and improve the mobility of paralyzed limbs. With the goal of eventually using the HT in the Japanese Experiment Module (JEM) of the ISS, the system design was evaluated in relation to the following: stimulation conditions for safer use, application of a moistened silver electrode, electromagnetic compatibility (EMC) of developed stimulators and electric field emissions from the stimulated human body, a HT simulation of an astronaut floating in the JEM, and influence of HT-induced motion of an astronaut fixed in the JEM on the ISS.