Exercise Physiology in Extreme Environments - Essay Example

Exercise Physiology in Extreme Environments Many athletes and coaches have generally accepted the idea that traditional altitude training benefits sea-level endurance performance. Altitude acclimatization invokes some physiological changes which are similar to those which accompany endurance training. This is the evidence used as the basis of the hypothesis that altitude training improves endurance performance at sea-level. The higher you go in the atmosphere, the thinner the air (Baker 1998). When the body is subjected to this hypoxic environment, adaptive processes attempt to facilitate the intake, transport, and use of oxygen (Smith, Sharkey 1984). The term hypoxia refers to a pathological condition in which the body is deprived of adequate oxygen supply (Wikipedia, 2006a). Physiologists have long been astonished by the changes that occur with adaptation to altitude as the circulatory system attempts to compensate for the increased hypoxia by enhancing certain characteristics. Common reasoning asserts that if the characteristics of circulation at altitude are better than those of sea-level, then sea-level performances should be enhanced among these athletes. For example, training at altitude, anywhere above 3000 meters, increases the body’s number of red blood cells, thus the blood’s capacity to carry oxygen is greater. It seems reasonable that this would enhance sea-level performance as the high altitude athlete’s body uses oxygen more effectively which enables that individual to run farther and faster (Sutton, 1994). However, these assumptions of high altitude training are just that. Contradictory evidence suggests that high altitude training is not only ineffective, but the physiological events that occur in the body as a result can be harmful. Ascent to high altitude is accompanied by a progressive fall in barometric pressure and an accompanying fall in the partial pressure of oxygen. “As low-level dwellers, we are optimally equipped for existence at normal air pressure of 760 mm of mercury, with an oxygen concentration of 21 percent. With increasing altitude, the concentration of oxygen remains the same, but the atmospheric pressure decreases and with this the partial pressure of oxygen falls. This means that the number of oxygen molecules per breath is greatly reduced and this in turn reduces the amount of oxygen available to the blood and tissues in the body” (Quinn, n.d.). The resulting decrease in arterial oxygen saturation (hypoxaemia) triggers a cascade of physiological disturbances that ultimately result in an increase in the production of red blood cells (RBCs), a process known as polycythaemia. The production of RBCs helps to improve the oxygen-carrying capacity of the blood, and hence maximal oxygen uptake (VO2 max) (McConnell, 2005). VO2 max is defined as the maximum volume of oxygen that a person can metabolise during exercise (Wikipedia, 2006b). As exercise intensity increases so does the intake of oxygen. The faster a person runs, for example, the more oxygen must be consumed to sustain the pace. VO2 max is the point where the body cannot increase the amount of oxygen it consumes and utilises, despite an increase in exercise intensity. High altitude is accompanied by a decrease in the partial pressure of oxygen which, in turn, leads to a reduction in the driving pressure for oxygen transport and a corresponding fall in VO2 max. An increase in altitude of as little as 600m has been shown to decrease the performance of cyclists in a five-minute cycle power test. Thus, it is easy to see that one confounding influence on the outcome of altitude training is the progressive decline in VO2 max, which compromises training intensity, leading to ‘detraining’ at altitude (McConnell, 2005). When athletes who live at sea-level train in altitudes, they begin to train less intensely and at slower speeds than they would normally at sea level. Training more slowly is definitely not the way to set world records. Those that continue to subscribe to high altitude training must therefore believe that the higher the better. It has been shown, however, that this is not the case as the body reacts negatively to high altitudes where a person can succumb to a variety of symptoms commonly known as Altitude Illness. Physical conditioning does not necessarily protect you from developing mountain sickness, but proper acclimatization often reduces the risk. “Acclimatization is the process by which the body slowly adapts to the decreasing availability of oxygen at altitude. This process is slow and takes several days to weeks to occur” (Quinn, 2006). Altitude levels 1500 - 2500m Medium Altitude Adaptation is sufficient 2500 - 5300m High Altitude Adaptation is not sufficient - acclimatisation is necessary (AMS) 5300 - 8848m Extreme Altitude Acclimatisation is not possible Table A: Acclimatisation at the different altitude levels. Source: Quinn, n.d. A faster breathing rate, (hyperventilation) shortness of breath, increased urination and broken sleep are common symptoms when at high altitudes. “Unfortunately, hyperventilation also blows-off excess carbon dioxide from the body which has the potential to disrupt acid-base balance of the tissues and contribute to altitude sickness. Considerable body water is also lost with high ventilation rates leading to a relative state of dehydration” (Graetzer, n.d.). These changes are the body’s natural reaction to the reduced availability of oxygen in the atmosphere, a thinner atmosphere. To obtain all the oxygen the body needs, a person finds it necessary to breathe faster and deeper, but even with a faster breathing rate the person finds it increasingly difficult to acquire adequate amounts of oxygen to the lungs and muscles. Fatigue sets in much sooner at higher altitudes. “There are also some very complicated changes that occur in your fluid balance as you acclimate. One of these is a more concentrated blood level and you will find you urinate more frequently” (Quinn, 2006). Adverse changes in the body continue to take place with prolonged exposure to altitude. The problem of altitude illness starts when acclimatization does not keep pace with an ascent to higher altitude. Illness symptoms are more extreme and serious than those of acclimatization. Headache is the first warning sign of altitude illness. Other symptoms may follow and include hyperventilation, loss of appetite, nausea or vomiting and fatigue (Quinn, 2006). Barometric pressure decreases as a person ascends further up through the atmosphere and every breath contains fewer and fewer molecules of oxygen. A person must breathe harder to obtain oxygen. This is particularly noticeable with physical exertion such as excising or training. “When acclimatization lags appreciably behind ascent, various symptoms occur. Acute Mountain Sickness (AMS) denotes the bodys intolerance of the hypoxic (low oxygen) situation” (Dietz, 2000). AMS includes a range of illnesses, from slight to life-threatening. At the severe end of this spectrum is High Altitude Pulmonary Edema (HAPE) caused by physical exertion at high altitude, rapid ascent and/or exposure to cold (Qazi, 2004). Signs of HAPE include congestion, extreme fatigue and breathlessness even while at rest. If the affected person does not immediately descend, the decision may be fatal. High Altitude Cerebral Edema (HACE) is when the brain swells and ceases to function properly. “HACE, once present, can progress rapidly, and can be fatal in a matter of a few hours. Persons with this illness are often confused, and may not recognize that they are ill. The hallmark of HACE is a change in mentation, or the ability to think” (Dietz, 2000). The person affected may experience confusion, changes in behavior or exhaustion. An easily recognizable characteristic of HACE is loss of coordination, referred to as ataxia. This is a staggering walk that is identical to the way a person walks when very intoxicated on alcohol. “To test for this abnormal walk, have the sick person do a straight line walk (in medical speak this is called the "tandem gait test"). Draw a straight line on the ground, or have them follow a crack in the teahouse floor. Have them walk along the line, placing one foot immediately in front of the other, so that the heel of the forward foot is right in front of the toes behind” (Dietz, 2000). If the affected person struggles to stay on the line, they should be presumed to have HACE. As with HAPE, failure to quickly descend at once may prove a fatal decision. “People with HACE usually survive if they descend soon enough and far enough, and usually recover completely. It is common for persons with severe HAPE to then also develop HACE due to the extremely low levels of oxygen in their blood (equivalent to a continued rapid ascent)” (Dietz, 2000). HAPE generally occurs 1-4 days after rapid ascent to altitudes in excess of 2500 m (8000 ft). Young people and previously acclimatized people re-ascending to a high altitude following a short stay at low altitude seem more predisposed to HAPE (Qazi, 2004). “Epileptic patients who have been stable for years and eventually gone off their medications have had seizures within a short time of traveling to high altitude. People with no known seizure disorder have had their first ever seizure at high altitude, usually within a few days of arrival. Shlim and Meijer documented three people who had previously unsuspected brain tumors who all became severely symptomatic within 24 hours of exposure to altitude ranging from 9,000 to 13,000 feet. All of the patients had severe symptoms at altitude that persisted after they returned to low altitude” (Shlim, 1997). So why do so many endurance athletes train at altitude? Altitude does have one positive effect for endurance runners; it builds up the bloods oxygen carrying capacity. However, many athletic researchers claim the best strategy is to live at high altitude but to train at sea level, that this is more effective than training at a high altitude and competing at lower elevations. Training at a high altitude, as some conclude, is only beneficial prior to competitions conducted at similar elevations. High altitude training has little or no effect on competition at a lower altitude. Studies conducted at the Olympic Training Center at Colorado Springs (elevation 6,500 feet) examined the effect of high and low altitude training on exercise performance and have concluded that exercise at altitude can be severely restricted following conditioning at sea level (Graetzer, n.d.). And more than that, “altitude also stimulates an increase in heart rate and cardiac output to increase blood circulation by the muscles to unload oxygen and pick-up carbon dioxide and back to the alveoli to reverse these exchanges. This serves to compensate for the bloods reduced oxygen saturation but also provides more stress to the heart which may affect people predisposed to heart disease” (Graetzer, n.d.). Males and females alike are similarly affected. Anyone regardless of age and fitness venturing to higher altitudes can develop Acute Mountain Syndrome (AMS). Catherine Quinn (n.d.) quotes Ravenhill (1913) as saying: “There is in my experience no type of man of whom one can say he will or will not suffer from AMS. Most of the cases I have instanced were young men to all appearances perfectly sound. Young, strong and healthy men may be completely overcome.” References: McConnell, Alison. (2005). “Altitude Training Effects: Is Altitude Training a Waste of Time and Money?” Peak Performance [online]. Available from < http://www.pponline.co.uk/encyc/altitude-training-effects.html> [13 January, 2006]. Baker, A. and Hopkins, W.G. (July 1998). “Altitude Training for Sea-Level Competition.” Sportscience Training and Technology [online]. Available from [13 January, 2006]. Dietz, Thomas E. (16 August, 2000). “All About Altitude Illness.” High Altitude Medical Guide Emergency & Wilderness Medicine [online]. Available from [13 January, 2006]. Graetzer, Dan. (n.d.). “High Altitude and its Effects on Exercise Performance.” Sumeria [online]. Available from [13 January, 2006]. Qazi, Samia. (7 October, 2004). “Pulmonary Edema, High-Altitude.” EMedicine [online]. Available from [13 January, 2006]. Quinn, Catherine A. (n.d.). “High Altitude.” Mountaineering Council of Ireland [online]. Available from [13 January, 2006]. Quinn, Elizabeth. (2006). “How to Recognize, Prevent and Treat Symptoms of High Altitude Illness (AMS).” Your Guide to Sports Medicine [online]. Available from < http://sportsmedicine.about.com/cs/altitude/a/aa100802a.htm?terms=altitude> [13 January, 2006] Shlim, David. (1997). “High Altitude Medical Advice for Travelers.” Clinic Travel Medicine Center [online]. Available from [13 January, 2006]. Smith, M.H. and Sharkey, B.J. (1984). “Altitude Training: Who Benefits?” The Physician and Sportsmedicine [online]. v. 12, pp. 48-62. Available from [13 January, 2006]. Sutton, J. R. (1994). “Exercise training at high altitude.” Swimming Technique, February-April, 12-15 [online]. Available from [13 January, 2006]. Wikipedia contributors. (2006). “Hypoxia (medical).” Wikipedia, The Free Encyclopedia [online]. Available from < http://en.wikipedia.org/w/index.php?title=Special:Cite&page=Hypoxia_%28medical%29&id=35274372> [13 January, 2006]. Wikipdeia contributors. (2006b). “VO2 Max.” Wikipedia: The Free Encyclopedia [online]. Available from [13 January, 2006]. Read More