Discussion

In this study of five triathletes, their experience in the hyperthermia chamber clearly replicated the overheated feeling, exhaustion, and nausea that occurred during their Ironman event. During the one hour study, serum osmolality levels did increase, as did electrolyte levels, but not to the degree to signify dehydration. Cortisol levels increased drastically, and large changes in glutathione levels were also observed, which confirmed that the high body core temperatures were causing significant distress to the participants. Venous blood alkalosis is the most likely blood parameter responsible for the unpleasant feelings associated with the hyperthermia. While there were some changes in the various blood biochemical parameters, the most notable changes were in venous serum blood pH. As time elapsed and core body temperature increased, the participants’ blood pH climbed from its initial average of 7.55 to 7.67 after one hour in the hyperthermia chamber.

Blood pH and its relationship to exercise have been studied by looking at opposite ends of the spectrum. Anaerobic exercise, short duration, high-intensity exercise, the type sprinters and power-lifters perform, for example, produces some level of metabolic acidosis in the athlete, due in part to the production of lactic acid in the muscles. Aerobic exercise, the type that triathletes and marathon runners perform, causes the athlete to lose large amounts of sweat containing electrolytes, particularly chloride, leading to metabolic alkalosis. This anion, chloride, is lost in large amounts (salty taste of sweat) during long-duration aerobic exercise. Severe metabolic alkalosis is feared in pediatrics, especially in neonatal settings, because sweating in infants can lead to excessive chloride wasting,²¹ whether due to high ambient temperatures or diseases like cystic fibrosis, where one symptom of CF is very salty sweat because of inordinate amounts of sodium chloride being lost through the skin.²² Alkalosis is also monitored in the veterinary arena, especially in performance animals like horses. Prolonged slow work causes heavy sweat loss and pH rises, causing poor performance, nervousness, and muscle cramping.23 Thus a thoroughbred horse sprinting in a short race would be at risk of acidosis, while a show horse in dressage would be subject to alkalosis.

Venous blood pH, which seemed to have the most influence on the subjects’ performance, or their “ability to run,” was measured because the body’s enzymes work optimally within a narrow range of blood pH. These enzymes are the catalysts which speed up the reactions in the oxidative phosphorylation process by which the body produces energy in the mitochondria of the cells.²⁴ Basically all metabolic processes in the body are run by a series of enzymes, all of which function at an optimum pH. As with all enzymes, extremely high or low pH values can lead to a complete or partial loss of activity of a particular enzyme.²⁵ An animal study using frogs looked at the enzyme phosphofructokinase, involved in the one of the rate-limited steps during oxidative phosphorylation in reptilian and human metabolism. It was found that a small shift in pH caused this enzyme to lose its ability to function, thereby dramatically slowing down metabolism.²⁶ When pH fluctuates outside its very narrow optimal range, enzyme activity slows down. As enzyme activity slows, the body’s ability to make energy is also slowed and energy reserves suffer.²⁷ Energy production and athletic performance go hand-in-hand. If energy production wanes for whatever reason, athletic performance will logically drop.

Anyone who has watched an Ironman Triathlon race on television, spectated one, or completed one knows that this is one of the toughest one-day endurance events in the world. Obviously an athlete’s physiology during a 10 to 17 hour event like the Ironman will be severely challenged. As such, multiple parameters were evaluated in this study. Endurance athletics cause drastic fluctuations in mineral and hydration levels. Mineral levels such as potassium, sodium, magnesium, and calcium were evaluated in this study. These changed very little in the five athletes we studied, so changes in mineral levels could not have accounted for the drastic changes in the athletes’ demeanor and feelings in the hyperthermia chamber. To evaluate hydration levels, urine specific gravity and serum osmolality were checked. These both increased (along with hemoglobin and hematocrit), suggesting the athletes were starting to get water depleted but stayed within the normal range, thereby eliminating dehydration as the cause of these participants’ symptoms subjected to hyperthermia. Urine pH was looked at because it can give insight as to whether or not a subject is experiencing metabolic or respiratory acidosis if the urine is too acidic. It may also give an indication of respiratory alkalosis due to hyperventilation if the urine is too alkaline.²⁸ As cellular respiration is increased dramatically during high-level athletics, urine pH was measured in this study. Urine pH generally stayed the same, even though the blood pH became very alkaline.

Additional cellular damage occurs with the increase of cellular respiration in endurance events, challenging the athletes’ antioxidant reserves. Glutathione levels in the red blood cells and plasma were studied, along with the anti-oxidant assay, measuring the enzymes glutathione peroxidase, catalase, and superoxide dismutase. The anti-oxidant assay results before and after hyperthermia exposure were relatively unchanged, while glutathione levels were drastically affected. Glutathione in the red blood cells and plasma were measured because of the role of glutathione in preventing cellular damage caused by free radicals produced during cellular respiration.^{29, 30} Glutathione is also involved in the detoxification of harmful compounds, in the formation and maintenance of disulfide bonds in proteins and in transport of amino acids across cell membranes.³¹ The large change in glutathione levels, along with cortisol, the main stress hormone, give credence to the notion that the five athletes, truly were stressed and enduring excessive tissue damage in the hyperthermia chamber. As the Ironman Triathlon event is extremely stressful, hormones such as cortisol will be secreted. Cortisol is the predominant glucocorticoid in the body. It is an essential component of adaptation to severe stress. The action which supports this stress reaction is gluconeogenesis,³² the synthesis of glucose from molecules that are not carbohydrates, such as amino and fatty acids.³³ This is important in endurance events. Since muscle tissue is damaged and causes inflammation, C-reactive protein (CRP) was also checked. The CRP test is a sensitive and quantitative measurement used to detect low-grade inflammatory responses, evaluating the severity and course of an inflammatory process; it is an abnormal protein, virtually absent from the blood of healthy people,³⁴ or those not participating in some type of endurance event. In this study, the CRP values changed very little, which may be due to the fact that the athletes did not receive enough tissue damage to change this value.
 
Hyperthermia is, of course, related to a spectrum of heat illnesses, with the most severe being heat stroke. Severe heat stroke denatures proteins, destabilizes phospholipids and lipoproteins, liquefies membrane lipids, leading to cardiovascular collapse, multi-organ failure, and ultimately, death.³⁵ The level of heat illness experienced by the study participants, however, did not approach heatstroke status, either in competition, or in the infrared chamber. The ambient temperature in the races and the generated heat in the chamber were factors in the subjects’ blood becoming alkaline, but we must not forget the heat generated by their bodies during an actual competition. Strenuous physical activity can increase heat production more than 10-fold to levels exceeding 1000kcal/h.³⁶ Skin is the major heat-dissipating organ. At high ambient temperatures, evaporation, through sweating, becomes the most effective means of heat loss. So while an athlete can avoid acute heatstroke through proper hydration before and during a race, and hopefully having an efficient eccrine system, the negative effects on performance from rising blood pH levels are something else for the athlete to consider.
 
In this study as temperature and pH increased, mental clarity decreased 20.2% after 30 minutes, and 60.6% after 60 minutes in the chamber. Nausea increased by 10.6% midway through the experiment, and ended with an overall deficit of 40.6%. Running ability decreased by 60% midway through, and by over 95% at the conclusion of the study. While the exact chemical cause of these symptoms can not be proved in this study involving five people, venous blood alkalosis is one factor to consider. Basic biology and chemistry notes that the farther away from “optimum pH” for a particular enzyme, the less efficient that enzyme will work,³⁷ which most likely will result in a suboptimal performance for the athlete involved in high-level competition.

Future studies testing venous blood alkalosis would necessitate a larger sample size and would ideally involve athletes before and after actual competition in the heat. An apparent application of these results would be the control of blood alkalosis to enhance athletic performance for the athlete competing in the heat.