Phil Carvil, PhD
MedTech Cluster Development Manager at STFC, and all-round fitness and Space fanatic!
As mentioned in my previous blog, my major area of interest is human physiology and how the human body responds to exercise stimulus, especially in extreme environments, such as in Space.
On Earth, right now as you sit, stand or walk around, you are being ‘loaded’ by gravity. Your body is designed and has developed to enable you to function on Earth. Your muscles and their deployment (larger muscles in the legs) are designed to let your resist the force of gravity. Your heart and its systems are designed to pump blood in response to signals of how your body is oriented, i.e. when you are laying down as opposed to standing up. The spine is curved in response to gravity. It’s amazing when you think about how much your body works just to maintain itself in gravity – now think about what happens in space when you have microgravity, which means very little gravity.
It is documented that when you are in low Earth orbit (microgravity) for extended periods of time your body adapts. Part of this response is to diminish some of the muscle and its functionality, especially in the lower limbs. When you think about it, this makes complete sense. You work your legs just getting out of bed in the morning – imagine if you didn’t even need to do that? When you undertake physical training, particularly resistance training you build those muscles, they get bigger, stronger in response to the change in demand placed upon them. These muscles need a reason to adapt and change - in microgravity without that demand or need, they atrophy, as they require a lot of energy to maintain. Without that need, the body in its own very efficient way changes. That is why exercise forms such a key component of astronaut training pre-, during and post-flight.
Astronauts receive the assistance of an incredible support team of physiologists, trainers, physiotherapists, scientists, doctors, psychologists, nurses, engineers and mission specialists (to name just a few). Specialist equipment has been designed to enable them to train in space, based on key exercise training modalities on the ground. For aerobic exercise they employ both cycling on a device called CEVIS (Cycle Ergometer with Vibration Isolation and Stabilization System), and treadmill-based walking/running on a modified treadmill that ‘pulls’ them on to the belt as they run COLBERT (Combined Operational Load-Bearing External Resistance Treadmill), otherwise they would not get that critical ‘contact’ time with the belt. It is that contact, that impact, that is so important for sending a mechanical signal through the body to enable adaptations to happen (see video below, courtesy of NASA).
Resistance training also forms a critical component of their training, providing a mechanical stimulus and signal to the body cells and systems. Normal weights as we use on Earth would not work in space without gravity, and therefore, a device is used that employs hydraulics to provide that resistance force, which can be modified for various exercises (ARED - Advanced Resistive Exercise Device). The principles of why an astronaut trains are the same in space as they are on Earth – to stay fit, healthy and functional. The only difference is how they do this, the greater imperative to undertake exercise and the insights gained.
We have learned so much about how the body changes in space from the astronauts that have remained there for periods of time, shaping our understanding of the human form, but also adding to our knowledge of how to keep it healthy. As we begin to think about establishing long-term habitats on other celestial bodies, such as Lunar or Martian habitats later this century, the same key questions about how we keep ourselves, fit, healthy and functional will be just as important to address. So the next time you’re undertaking a training session, be it a walk in the park, a group exercise session in the gym, or even just defying gravity, look up and think – someone up there is training too!