International SportMed Journal - Volume 6, Issue 4, 2005
Volume 6, Issue 4, 2005
Author Gilles ClementSource: International SportMed Journal 6, pp 185 –198 (2005)More Less
<I>Objective:</I> There are a number of physiological changes which occur in astronauts in both short- and long-duration space missions, including nausea and spatial disorientation, orthostatic hypotension, muscle atrophy, bone loss, increased cancer risk from space radiation, and many others. This review examines the procedures and methods, also called countermeasures, used to moderate these changes. <br><I>Data sources:</I> The information in this paper is taken from a review of articles and book chapters (Source: PubMed and MEDLINE, years covered 1995-2005). <br><I>Conclusions:</I> The countermeasures currently adopted to counteract the effects of microgravity conditions on board space missions aim at stimulating a particular physiological system: the treadmill, the cycle ergometer and the interim resistive exercise device primarily for muscles and bones, intermittent venous pooling and fluid loading for cardiovascular responses, and pharmacological manipulations for space motion sickness. However, all have only limited success. Indeed, despite extensive in-flight exercise, most astronauts experience difficulties in standing, walking and getting oriented for several days after landing. This poses a serious problem in case of an emergency landing on Earth or a landing on Mars after a long-duration spaceflight. Studies are being conducted for the search of more effective countermeasures that address all physiological systems across the board, such as artificial gravity generated by short-arm centrifugation.
The impact of space flight on the human skeletal system and potential nutritional countermeasures : review articleSource: International SportMed Journal 6, pp 199 –214 (2005)More Less
Bone loss is a critical health issue during space missions. Much in-flight and ground-based effort has been expended to understand and counteract this phenomenon. Although the more obvious countermeasures have been tested, with exercise and pharmaceutical therapies at the forefront, nutrition and dietary management has been largely untested. Some of the recent findings on exercise and pharmacotherapies, as well as ground-based data highlighting a few areas where nutrition has a clear effect on bone health, are reported in this review. One area highlighted here is the role of protein in acid-base balance and how this many affect bone during space flight. Finding a countermeasure for space flight-induced bone loss will benefit space travellers as well as help scientists better understand bone physiology in general, for the benefit of individuals with bone diseases and immobilised individuals.
Author Martin BurtscherSource: International SportMed Journal 6, pp 215 –223 (2005)More Less
With increasing altitudes, athletes will experience marked decreases in endurance performance; occasionally they will develop high-altitude illness, and in rare cases, even life-threatening forms. Thus, the understanding of the physiological basis of performance diminution and the development of high-altitude illnesses is important for the implementation of appropriate preventive and therapeutic measures. <br>Aerobic exercise performance decreases upon ascent to altitude, whereas anaerobic performance remains unchanged. Typically, sub-maximal but not maximal exercise performance improves following 1-3 wk of acclimatization due to an increase in arterial oxygen saturation and haemoglobin concentration from increasing ventilation and decreasing plasma volume, respectively. The falling PiO<sub>2</sub> and the related decrease in PAO<sub>2</sub> and SaO<sub>2</sub> with increasing altitude not only affect exercise performance but are also mainly responsible for the development of high-altitude illnesses. <br>Whereas acute mountain sickness (AMS) represents the most common illness, which is benign and self-limiting in nature, high-altitude cerebral edema (HACE) and high-altitude pulmonary edema (HAPE) are rare but severe life-threatening illnesses. <br>Beside the most important general preventive measures like pre-acclimatization, slow ascent to altitude, sufficient intake of fluid and carbohydrates, and avoidance of alcohol and nicotine, some drugs such as acetazolamide, COX inhibitors, dexamethasone, nifedipine or salmeterol have proved efficacious in the prevention of altitude illnesses in subjects susceptible to them. The same drugs, oxygen, hyperbaric chamber, and evacuation to low altitude are effective for treatment of high-altitude illnesses.
Author Myra A. NimmoSource: International SportMed Journal 6, pp 224 –235 (2005)More Less
<I>Objective:</I> This review presents an overview of the literature relating to aspects of exercise in a cold environment. <br><I>Data sources:</I> MEDLINE, PubMed and ISI Web of Knowledge were used to search the literature base with no restraint on the date of publication. The review was completed in September 2005 and reflects the literature until that point. The keywords used were: cold, exercise and performance. <br><I>Study section:</I> Over 60 references are cited. <br><I>Data extraction:</I> Studies which have robust experimental procedures are cited. Where there are possible limitations, these have been identified. <br><I>Data synthesis:</I> Exercise can be used to offset heat loss in cold environments; however, the intensity must overcome the negative effects of the exercise, which include losing the insulative capacity of the resting muscle and any insulative boundary layer around the body. However, there is a metabolic cost of this increase in activity. At moderate intensity activity, a temperature of 3-10<sup>o</sup>C is advantageous, whereas in low-, high- and intermittent activities, a cold environment is deleterious to performance. The predominant fuel at all intensities would appear to be carbohydrates and dietary strategies should reflect this. <br><I>Conclusion:</I> Speed swimming should be undertaken at temperatures around 28-30<sup>o</sup>C, whilst moderate intensity exercise in air is optimised around 3-10<sup>o</sup>C. At environmental temperatures below 0<sup>o</sup>C fat utilisation is inhibited and at all temperatures the dominant fuel is carbohydrate. Acclimatisation to cold is possible but more work is required to prescribe acclimation protocols.