A second aim of the study will be to provide Mark with a number of specifically designed exercises that he will be able to do both before he leaves for space as well as while he is in space. Previous research has shown that although there is no muscle damage that occurs during space flight - predominantly because there is no gravity to load the muscles – as soon as the astronauts arrive back to earth they experience muscle pain and stiffness. This muscle pain is similar to that which we experience on earth after participating in any unaccustomed or strenuous exercise, and is caused by miniature tears to the muscle fibers. This pain usually occurs a little while after the exercise, and hence it has been referred to as delayed onset muscle soreness (DOMS). Other studies have shown that if an exercise causes this kind of response, it is likely that there may be some protective effect on that muscle and that if the same exercise is performed on a second occasion, the pain and muscle damage may be slightly less. The practical importance of these different studies will be in the context of future space flights. We are hoping to identify countermeasure exercises that will assist in lessening the negative effects of space flight on both the cardiovascular system and muscle structure and function.
The third aim of the study involves a component of space travel that has been extensively studied is that of energy balance and energy expenditure. The use of the doubly labeled water technique, a very accurate means of measuring total energy expenditure (TEE), has previously been validated in space with highly accurate results. It has been found that astronauts lose a significant amount of body weight during space flight. This is attributed to the maintenance of energy expenditure while dietary intake is significantly reduced, resulting in a negative energy balance.
Another method for measuring TEE, and one that has not yet been validated in space, is that of the heart rate monitoring (HRM) method. Heart rate monitors provide relatively inexpensive, non-invasive tools that allow for the accurate measurement of energy expenditure, provided the person has been individually calibrated so that they have created their own heart rate-energy expenditure relationship. If HRM is proved to be an accurate measure of TEE in space, where there are known cardiovascular changes in heart rate, when compared to the doubly labeled water technique, then this should strengthen the accuracy of this method on Earth as well as provide for a much more user friendly measure of energy expenditure during space flight.
“The Ethics and Research committee of the University of Cape Town, Faculty of Health Sciences, approved the study and informed consent has been obtained from the subjects before the commencement of the trial.”
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