Tri Tri Again: The Physiology of Triathlon

Abstract

The cardiovascular system plays an essential role in any endurance event. The Ironman Triathlon is a long distance event that is made up of a 2.4 mile swim, a 112 mile bike, and a 26.2 mile run for a total of 140.6 miles. Each segment of an Ironman Triathlon poses unique challenges to the cardiovascular system. In order to complete such a monstrous race cardiovascular adaptations occur during the chronic stress of training, and the body also makes acute adaptations during the metabolic stress of the race itself. These alterations of the heart, blood vessels, and the blood make the body more efficient at transporting oxygen and nutrients to the muscles via the circulatory system, at extracting oxygen and nutrients from red blood cells and into the tissues, and at maintaining homeostasis. The results of these changes are higher maximum heart rate, increased oxygen extraction, higher capillary bed density, higher mitochondrial density, increased VO2 max, increased cardiac output, better thermoregulation, and non-pathological hypertrophy of the heart. While an excessive amount of long-term vigorous endurance activity can have adverse impacts on the cardiovascular system, the body is surprisingly capable of racing such a long distance with the proper training adaptations.