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The tactical squad

Friday, January 22, 2016
Dirt Under the Nails

Space: the final frontier…and certainly a very new and different one for fitness! The astronaut athlete is a new athletic domain, an expansion into the still very young world of occupational physiologic training. This world explores the relatively new field of tactical strength and conditioning, which centres around an understanding of the physical demands of one’s job. 

The people involved in these professions are called tactical athletes whose jobs require specific physical functions for which they must train. Firefighters, law enforcement, search and rescue and military professionals need specialised physical training in order to perform their physically demanding jobs.

Astronauts are also tactical athletes. However, their situation is very different from all other tactical professions. They must perform in microgravity conditions for long periods of time that can vary from a few weeks to six months at the International Space Station (ISS).

Gravity is the terrestrial force which allows us to stay on the ground. However, in places like the moon and the ISS, the gravity is minimal and therefore astronauts “float” in Space. This microgravity condition has some significant maladaptive effects on the body.

On Earth, our own body weight provides our muscles and bones with resistance against which they must work and move. Our muscles and bones move the load of the body against the downward force of gravity. This resistance provides a strengthening stimulus and can be increased by adding weights. For example, in a squat, gravity pulls the body down. Muscles of the legs and core must push the body weight up against the downward force of gravity. The weight of the body under gravity provides a strengthening stimulus. 

However, because we float in microgravity environments, body weight is negligible. Gravity provides no resistance to move against, so there is no strengthening stimulus for the bones and muscles. As a result of this reduced mechanical loading, deconditioning occurs and astronauts actually lose significant muscle strength, bone mass and cardiovascular conditioning.

Astronauts can lose six per cent of muscle volume after an eight-day flight and up to 48 per cent loss has been recorded after a six-month exposure to microgravity. These losses are similar to 90 days of bedrest on Earth.

However, a certain level of strength and fitness is required to perform certain tasks in space. For example, emergency egress upon return to Earth on land or water requires significant power, strength and muscular endurance in order to perform a variety of pushing, pulling and lifting or holding tasks to escape from the space vehicle. 

A 10km walk on the moon demands that the astronaut have considerable cardiovascular endurance. With the intended exploration of Mars, construction tasks will call for strength and muscular endurance, and the ability to perform other types of extra vehicular activities requires cardiovascular endurance and strength.

These components of fitness suffer in microgravity. Astronaut Strength and Conditioning Specialists (ASCS) are challenged to find ways to overcome these effects so that astronauts can remain fit enough to perform important functions during their missions. 

There has been very little research done on astronaut fitness in space, which makes program design and training even more challenging. Monitoring astronauts in space during exercise is possible through the use of computers and the downlinking of information to Earth. However, this is often unreliable because of equipment malfunction. 

In addition, designing specific exercises on Earth for a microgravity environment proves very difficult. ASCSs design in-flight programs based on individual fitness testing on Earth. Remember that a crew member’s body mass no longer provides a strengthening stimulus in microgravity.

Therefore, tests are a poor indicator of how the astronaut’s body will respond in microgravity. As a result, much of the program development is guesswork and quite conservative to allow the astronaut’s body to adapt to the in flight conditions.

Another problem is the equipment. Specialised fitness machines have been designed to operate under microgravity conditions, and are therefore not optimal for training in Earth’s gravity. Although astronauts perform familiarisation sessions on these machines prior to flight, most of their preflight fitness training occurs on traditional exercise equipment, which does not optimally prepare the body to cope with microgravity.

But why should all this matter and why is it so important to research fitness in astronauts? Like firefighters or military personnel, there is a certain level of fitness below which task execution is impaired, and this can mean life or death. Furthermore, with the looming possibility of missions to Mars and beyond, missions may get longer and microgravity’s effects on the human body more significant.

It is critical that astronaut fitness be maintained above the minimum level for task execution to ensure mission success and to maximise the potential for future mission completion. This is one small step for athletes, but one giant leap for strength and conditioning professionals. 


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