Hyperthermia Induces Venous Blood Alkalosis: A Study in Five Ironman Triathletes

Introduction

Body temperature regulation is an important component of any exercise or training regimen. This is especially true for the endurance athlete competing in a high temperature environment. If the ambient temperature becomes too high, the athlete reaches a point where elevated body temperature and dehydration ensue. As a result, symptoms such as cramping, nausea, dizziness, and weakness appear. At this time, athletic performance also begins to decrease.^1-4 Fortney and Vroman, in their study on exercise performance and temperature control said, “…the effect of high ambient temperatures on exercise performance is most evident in prolonged submaximal exercise,”⁵ as is the case in Ironman Triathlons. These researchers and others have primarily examined the effects of body core temperature in athletes and how it relates to decreased blood volume and dehydration, the shunting of core blood reserves to the athlete’s peripheral surface and hypothalamic thermal regulation.
 
It has been concluded that optimal athletic performance, especially in endurance activities such as running and cycling, is achieved in moderate external temperatures.^{6, 7}
A study featured in the New York Times showed that runners perform best in temperatures ranging from 41 to 50 degrees Fahrenheit.⁸ Nielsen, et al, in their paper on heat acclimation, measured core temperatures in eight athletes during 90 minute exercise periods and their experiment showed that in a cool environment of 18-20 degrees Celsius (64.4 to 68 degrees Fahrenheit) core temperature remained steady at 37.8 degrees C (100 degrees Fahrenheit); but in a 40 degrees C (104 degrees F) environment core temperatures rose to nearly 40 degrees C (104 degrees F) during the exercise period, with a corresponding decrease in performance.⁹ It has been documented that as external temperatures rise, so does an individual’s body temperature.^10-12 Consequently, as exercise in high temperatures persist and basal body temperatures continue to rise, pace and performance begin to decrease.^{13, 14} There is debate as to what physiological parameters in the blood cause levels to decrease in athletic performance with elevated temperature. Febbraio and Snow, in their study on the effect of heat stress on muscle energy metabolism during exercise, showed that sustained maximal voluntary muscle contraction with leg extensions attenuated in hyperthermic conditions.¹⁵ Galloway and Maughan, in their paper on the effects of ambient temperatutre on the capacity to perform prolonged exercise, said that reduced performance at 31 degrees C (88 degrees F) would most likely result from a reduction in central blood volume.¹⁶ This occurs as the body shunts blood peripherally for more efficient cooling. Several physiological parameters are affected by a rise in basal body temperature. Studies have examined various blood and urine test results and how they are affected by hyperthermia. Some have looked at how hyperthermia can result in a breakdown of electrolytes and can increase the use of muscle glycogen stores, likely resulting in decreased ability and increased fatigue.^17-19 Another study has shown hyperthermia to deplete intercellular glutathione content, thus possibly affecting immune response.20 While the endurance athlete competing in high heat is at risk for dehydration, for the athlete not dehydrated, the etiological basis for a decline in the athlete’s performance with hyperthermia is not known. The high external temperature fluctuations of the Ironman were simulated with the use of an infrared heating chamber in a controlled environment so that objective lab tests and subjective surveys could be administered to the participants.


MATERIALS & METHODS

This study examined how various biochemical parameters were affected in five Ironman triathletes subjected to hyperthermia via a hyperthermia chamber. The focus of this study was to look at several venous blood markers, including venous serum blood pH, osmolality and electrolytes, among others, to see which correlated best with the athletes’ hyperthermia and survey questions, including “body achiness” and “ability to run,” among others.


SUBJECTS

The subjects were five athletes, four male and one female, who had completed an Ironman Triathlon in 2005. The race is comprised of a 2.4 mile swim, 112 mile bike, and a 26.2 mile run with a cut-off time of 17 hours to complete the course. The five participants in this study each raced in extreme heat and humidity in the summer of 2005, and had sub-optimal performances leading to an inability to run during the marathon portion of the Ironman Triathlon. Each athlete had finishing times much higher than were anticipated because they had to walk an average 15-18 miles of the marathon because of being overheated. (See Table 1.)

The triathletes were asked to lay in a Far infrared (FIR) hyperthermia chamber within five months of completing their individual race event. The chamber was to simulate the conditions that caused them to stop running in the Ironman Triathlon. (See Figure 1.) Venous blood pH and electrolytes were measured every 15 minutes during the study and other variables at the beginning and the end of the study. The chamber used for the study was a BioTherm with 90+% Far infrared (FIR), 5-14 microns, peak 9.25-10.2 with an analogue controller.

The study design included a blood and urine test analysis of 17 different biochemical parameters and 13 self-reported survey questions pertaining to physical changes such as perceived temperature, mental clarity, nausea, energy level, and ability to run. The patients arrived at the clinic well-hydrated and having eaten a few hours prior to the study. Temperature, vital signs, blood tests, and survey questions were administered at the beginning and end of the 60 minute experiment, as well as every 15 minutes during the time that the participants spent in the chamber. Urine was only collected at the beginning and end of the trial, while blood was collected every 15 minutes via a venous catheter that remained in place.

The Nova machine used to test the venous serum pH and electrolytes was a Model 8 NOVA CRT machine designed by NOVA Biomedical Corporation. This laboratory machine at the primary author’s office read normal venous serum pH as 7.50-7.52.*

* The NOVA 8 CRT machine used in 2005 to analyze the venous blood pH used serum where the normal venous serum blood values were 7.50 to 7.52. Currently, the primary author’s lab now uses a NOVA Model CCX laboratory machine to analyze pH and it uses 7.36 to 7.38 as normal values, using whole venous blood instead of serum.

The blood samples were drawn into a marble-top tube (SST), allowed to coagulate for 30 minutes, then spun down in a centrifuge for 15 minutes. The serum was drawn off and immediately tested as the serum pH will change soon after being exposed to air.

The following biochemical variables were analyzed: venous blood pH, urine pH, glutathione rbc, glutathione plasma, anti-oxidant assay, (peroxidase, catalase and superoxide dismutase) cortisol, serum osmolality, urine specific gravity, white blood count, hemoglobin, hematocrit, platelets, ferritin, C-reactive protein, magnesium, potassium and calcium.