Astronauts and Exercise in Space: New Developments

Astronauts in space can spend hours exercising everyday. This aims to counteract the detraining effect of zero gravity conditions, which cause numerous physiological changes in the body. In muscle tissue, mass and strength decrease over time. The strength loss is especially evident in the muscles used to maintain posture, as they become largely irrelevant whilst floating around a spacecraft. Another significant effect of weightlessness is a decline is the density of bone, about 2% per month on average in space. This is less reversible compared to muscular changes and can have a particularly debilitating impact on return to earth.

Cardiovascular changes include increased blood return to the heart, due to less gravity-induced pooling of blood in the legs, while the “puffy faces” of astronauts develop due to this redistribution of blood in the body. Decrease in overall blood volume also develops and can cause low blood pressure and fainting when back in normal gravity environments. Many of the changes contribute to an overall drop in maximal aerobic capacity/fitness (VO2 Max). These negative adaptations to out-of-orbit travel have generated more and more research in designing relevant exercise programs and equipment, which seeks to safeguard the future health of astronauts.

Many different types of exercise and training have been used, some proving more effective than others. Heavy “push-pull” equipment attached to the spaceship, elastic bands/cords/belts and resistive equipment have been developed, while “strap-down” treadmills and bicycles are the norm. One device, currently in use, is the advanced Resistive Exercise Device (aRED). This works with vacuum cylinders, similar to bicycle pumps in reverse, which can apply loads up to 250 kg, according to NASA. In the example of a squat, the vacuum engages as the astronaut stands up, and when squatting back down, the vacuum draws the bar back to the origin position. The main concern, even with creating beneficial weight-bearing or elastic equipment, is still a lack of a total unilateral force acting on the body such as gravity. This leaves the decreases in bone density largely unaffected.

Latest research mainly revolves around creating artificial gravity-like forces. One design, dubbed “The Space Cycle” by researchers at the National Space Biomedical Research Institute (NSBRI), aims to accomplish this while aiming to be small enough and simple enough to operate and/or repair in a spacecraft. Picture a two-person, hanging merry-go-round. A rotating wheel sits on top of a central column. On one side of the wheel a reclining bicycle is suspended. Opposite is a cage-like platform, where a second person will stand. As the one astronaut pedals the bicycle, the whole apparatus starts to spin, causing both the bicycle and the platform to rotate around the column. As the rotational speed increases, both astronauts begin to experience effects of this centrifugal force as a form of artificial gravity.

Astronauts on long-term missions presently need approximately two hours of standard exercise a day to resist the effects of micro-gravity. The Space Cycle is seen as a way of reducing this exercise time, therefore increasing the productivity of those onboard. The weight of the mechanism, which is currently constructed out of steel, poses a problem. This may be reduced in the future using carbon composite materials, which may also slightly reduce its diameter, making it possible for use on the International Space Station.

Jed

Best Time of the Day to Exercise?

You may have noticed the poll we had running this last week or so. Is there science behind the results/preferences of when people prefer to train and exercise? Are certain times of the day better or worse than others? How much do psychological factors, rather than physical reasons, effect when people hit the gym?

There’s pros and cons both ways with regards to AM versus PM exercise and there are a lot of factors that influence specific exercise and its benefits (eg. nutrition, time). Everybody is effected in many ways by a “body clock” / circadian rhythm. This is an important mechanism for hormone release, activation of electrical activity in muscle, etc. This will have an effect on peoples’ exercise and training times. For example, many elderly folks prefer to exercise early in the morning, as they rise earlier, with an altered circadian rhythm and sleep patterns.

Mornings are generally better for exercise when trying to lose weight. One advantage of morning exercise is an elevated Resting Metabolic Rate (metabolism) through the day. This is accompanied by a phenomenon known as EPOC (Excess Post-exercise Oxygen Consumption) which can promote further fat loss over time. People that exercise in the morning also tend to have higher levels of adherence to exercise/training programs. Many ‘early birds’ also feel their mood is improved from the start of their day.
Some of us just aren’t “morning people” though and should rather find a time of day that we feel better about exercising. Mornings are also often accompanied by lower blood glucose, not so good for any weight/anaerobic training. Injuries are more common with morning training; body temperature is lower, flexibility is decreased and co-ordination with complex exercise techniques will be affected. Morning exercise has been shown to have a slightly higher risk of heart attack or stroke.

Two hormones that play a roll in exercise are Cortisol and Testosterone. Cortisol, a catabolic (breakdown) hormone, is highest within the body in the morning and decreases throughout the day. Testosterone, the main anabolic (build up) hormone, reaches its highest levels, relative to Cortisol, in the afternoon/evening.

Studies have shown that maximal strength reaches highest levels only after midday, with anaerobic and endurance ability peaking in the afternoon. This links with the higher anabolic hormone (Testosterone and Growth Hormone) state within the body to make afternoon/evening exercise slightly better for endurance, muscle mass and strength training. Body temperature rises steadily throughout the day, which makes sports performance generally better during late afternoon/evening. Exercise, especially at gyms, does tend to be more social in the afternoon and evenings too.
Exercising regularly in the PM does tend to be more difficult to maintain for some people as work commitments or distractions can interfere, although dealing with the day’s stress can be an added benefit of exercising at this time. Sleep is not generally affected by exercise, so evening exercise should be fine for most people.

Remember though, any exercise is better than no exercise at all.
Jed