It’s not easy being an astronaut. Not only do they have to work in cramped conditions and be isolated onboard space stations, they also have to worry about muscular atrophy during long space flights. Astronauts’ calf muscles are even known to reduce in volume during space flight.
So how can this be avoided?
A team of Japanese researchers delved into how astronauts can prevent these neuromuscular problems. They reviewed “how the morphological, functional, and metabolic properties of the neuromuscular system respond to lowered anti-gravitational activities,” according to a Doshisha University release.
Researchers first looked at human and rodent simulation models and saw how afferent and efferent motoneuron activity regulated neuromuscular properties. (According to osmosis.org, “afferent neurons carry information from sensory receptors found all over the body towards the central nervous system, whereas efferent neurons carry motor information away from the central nervous system to the muscles and glands of the body in order to initiate an action.”)
Their analysis shows that afferent neural activity plays a key role in regulating muscle properties and brain activity.
According to researchers, hindering anti-gravitational muscle activities causes the remodeling of the sarcomeres — the structural unit of muscles. This decreases their number and leads to muscular atrophy. Researchers add that exposure to low-gravity environments not only affects the muscles, but also the nerves. This is due to a reduction in the amplitude of the electromyograms in anti-gravitational muscles.
Because of gravitational unloading, motor control deteriorates. Astronauts had some difficulty walking after spaceflight, even though they exercised regularly onboard the International Space Station. While on the International Space Station, astronauts are required to use treadmills, bicycle ergometers, and resistance training equipment to counter the effect of reduced gravity on the neuromuscular system and safeguard their physical health. Despite exercising, it doesn’t always prevent neuromuscular changes.
Researchers report that “stimulating the soleus muscle adequately seems to reduce chances of atrophy.” They recommend that astronauts should walk or slowly run with rear foot-strike landing while exercising. They also say stretching the soleus is effective.
More challenges may happen when astronauts are exposed to a microgravity environment for six months or more — for example, a space mission to Mars. Researchers say their study “has major implications in the area of space research, with special emphasis on astronaut wellness.”
“Information from a unique perspective, as discussed in this review, may play an important role in the development of appropriate countermeasures against neuromuscular problems for future long-duration human space exploration missions,” the media release reads.
The journal is published in the Neuroscience and Biobehavioral Reviews.