astronaut in space

Exercise plan devised for astronauts to minimise muscular atrophy

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An action plan to prevent astronauts from experiencing muscular atrophy during spaceflight has been created by Japanese researchers.

Among the many functions performed by skeletal muscles, maintaining posture is one essential facet that allows us to move against the force of gravity.

But when these muscles do not experience gravity for extended periods of time, such as during space travel - an effect known as 'gravitational unloading' - they can start to atrophy leading to changes to their structure and properties.

Gravitational unloading causes deterioration of motor control, and walking difficulty has been observed in crews after spaceflight, even those who have exercised regularly during missions on the International Space Station (ISS).

Astronauts aboard the ISS 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. However, these exercise-based countermeasures are not always effective in preventing certain unwanted neuromuscular changes.

Researchers at Doshisha University reviewed how the morphological, functional, and metabolic properties of the neuromuscular system respond to lowered anti-gravitational activities.

They looked at human and rodent simulation models first and also saw how afferent and efferent motoneuron activity regulates neuromuscular properties. Afferent neurons carry information from sensory receptors of the skin and other organs to the central nervous system, such as the brain and spinal cord, whereas efferent neurons carry motor information away from the central nervous system to the muscles and glands of the body.

Their review suggests that afferent neural activity plays a key role in regulating muscle properties and brain activity.

Inhibiting anti-gravitational muscle activities results in remodelling of the structural units of muscles, resulting in a decrease in their number, further causing a decrease in force development eventually leading to muscular atrophy. The research found that exposure to low-gravity environments affects not only the muscles, but also the nerves.

Additional challenges may come into picture when astronauts are exposed to a microgravity environment for six months or more; for example, on a journey to or from Mars.

From the data, the researchers developed an exercise plan for astronauts designed to minimise muscular atrophy as much as possible.

In February, another study observed structural connectivity changes occur in the brains of astronauts following long-duration space flights.

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