HSE311 Applied Sport Science 1

Physiology of a TriathlonIntroductionA triathlon is an endurance event that requires participants to complete swimming, cycling and running legs in sequence, with success primarily determined by a competitor’s ability to sustain a high rate of energy expenditure for prolonged periods of time (1). As such, the sports science discipline of physiology is a key area pertaining to the sport of triathlon (1), with the aim of this presentation being to highlight its importance. Regardless of whether a triathlete is elite, sub-elite or amateur, the unique nature of the sport requires them to be proficient in three separate activities that are recognised sports in their own right (2). Successful triathletes are generally tall and thin with low levels of body fat to provide them with optimal power to surface area or weight ratios. Essentially, the less body mass carried by the athlete, the more efficient the oxygen and substrate delivery will be, and the better the performance (2).

MethodsI began my research with the Deakin University library catalogue, using a range of terms including ‘triathlon physiology’, ‘triathlon’, ‘triathlon requirements’ and ‘triathlon sports science’, however I was unable to find any sources of information that directly related to what I was looking for. Following this, I searched similar terms in the Google Scholar catalogue online, which produced a large range of sources on triathlon physiology and related topics, from which I selected nine relevant journal articles that provided me with good research information for my presentation.

ResultsThere are a number of key physiological parameters that dictate success or failure to some extent in the sport of triathlon. A traditional viewpoint (3) of endurance events in the past has identified maximal oxygen consumption (vo2 max), lactate threshold, movement economy and heart rate as being the four predominant areas that endurance athletes, such as triathletes, should focus on in their training regimes. Maximal oxygen consumption Maximal oxygen consumption, otherwise known as vo2 max, refers to the rate at which an individual can bring oxygen into the body and use it for energy production (3). A range of studies (3) have found insignificant differences between maximal oxygen consumption of long distance triathletes in cycling and running tests. In the majority of these studies, vo2 max wasrecorded at 55-60ml/kg/min, however these subjects have usually been amateur. The lack research in oxygen consumption during swimming legs of a triathlon can be explained by the logistical problems posed by conducting such tests in water (3). Lactate threshold Lactate threshold refers to the point at which lactate accumulation in the muscle is equal to it’s removal from the body, and generally signals an exceedingly high level of lactate production and fatiguing side-effects (3). Longitudinal assessments of triathletes both in training and competition have found that lactate threshold is lower in cycling stages as opposed to running legs of training or competition (4). However, other studies (5) have found that there is no significant difference in exercise intensity between the cycling and running legs of triathlon training or competitions. Heart Rate A wide range of studies (3) have found heart rate (beats per minute) to be significantly lower in cycling legs compared to running legs in triathletes. However, there has been some research conducted (6) that reported no change in the relationship between heart rate and percentage of vo2 max by using a treadmill or cycle ergometer test, indicating that exercise intensities of the two modalities are quite similar. Nonetheless, another study (7) has shown that heart rate corresponding to lactate threshold (previously discussed) is significantly higher in running compared to cycling. Movement Economy Movement economy can be defined by recording oxygen consumption at a certain speed, and thus an energy cost can be calculated by exercising at a certain speed and intensity. It has been reported (8) that any significant change in energy cost of exercise in triathletes can be attributed to any number of factors, including performance level, event distance, gender and age. In addition to this, a higher upper body mass in triathletes as opposed to elite long distance runners is said to explain the greater energy cost and decreased running economy in triathletes (3). Nonetheless, this parameter has undergone extensive analysis in triathletes with mixed and vague results.

ConclusionsFrom the vast amount of research done on the physiology of a triathlon, a number of key conclusions can be arrived at;

- Maximal oxygen consumption, lactate threshold, movement economy and heart rate should be the core focus of any triathlete wishing to improve their performance in such an event,- In order to be considered a sub-elite triathlete, generally an athlete must possess a vo2 max of 60ml/kg/min or above,- When attempting to increase lactate threshold of a triathlete, cycling is the recommended modality to achieve changes in this area, and- Research results into movement economy relating to triathletes is vague at best, however generally athletes with a leaner body mass will generate less of an energy cost during running and cycling legs within a triathlon.

References1. O’Toole ML, Douglas PS. Applied Physiology of Triathlon. Sports Med. 1995;19(4):251-267. 2. Sleivert GG, Rowlands DS. Physical and Physiological Factors Associated with Success in the Triathlon. Sports Med. 1996;22(1):8-18. 3. Millet GP, Vleck VE, Bentley DJ. Physiological requirements in triathlon. JHSE. 2011;6(2):184-204. 4. Kohrt WM, O'Connor JS, Skinner JS. Longitudinal assessment of responses by triathletes to swimming, cycling, and running. Med Sci Sports Exerc. 1989; 21(5):569-75. 5. Kreider RB, Boone T, Thompson WR, Burkes S, Cortes CW. Cardiovascular and thermal responses of triathlon performance. Med Sci Sports Exerc. 1988; 20(4):385-90. 6. Basset FA, Boulay MR. Specificity of treadmill and cycle ergometer tests in triathletes, runners and cyclists. Eur J Appl Physiol. 2000; 81(3):214-21 7. Zhou S, Robson SJ, King MJ, Davie AJ. Correlations between short-course triathlon performance and physiological variables determined in laboratory cycle and treadmill tests. J Sports Med Phys Fitness. 1997; 37(2):122-30. 8. Millet GP, Millet GY, Hofmann MD, Candau RB. Alterations in running economy and mechanics after maximal cycling in triathletes: influence of performance level. Int J Sports Med. 2000; 21(2):127-32.

9. Millet GP, Dreano P, Bentley DJ. Physiological characteristics of short and long distance triathletes. Eur J Appl Physiol. 2003; 88:427-430. Sam Ryan - 211338161

Figure: a 2003 study (9) that illustrated the high vo2max levels of elite male long distance triathletes.