Our interview today is with former ITU professional triathlete and coach Sara McLarty. Sara joins us a couple of weeks after ITU Stockholm August 26th. We'll talk a bit about that but we want to follow up on an article of hers that we read a few weeks ago on open water sighting technique and more.
Welcome to Episode #93 of the Mile High Endurance podcast. Mile High Endurance is your weekly connection to coaches, experts and pro athletes to help you reach your endurance and triathlon goals. We're your hosts Rich Soares, Khem Suthiwan and Bill Plock. We are glad you are joining us this week.
Thanks to Ben Hoffman for joining us last week and sharing his race stories and Kona prep with us. Khem and I had a lot of fun with that interview and got a lot of great quotes. Check out the 303Triathlon and read the Ben Hoffman article for more.
Lawrence E. Armstrong, Ph.D.
Department of Sport, Leisure, and Exercise Science
University of Connecticut
Complete heat acclimatization requires up to 14 days, but the systems of the body adapt to heat exposure at varying rates. The early adaptations (initial 1-5 days) involve an improved control of cardiovascular function, including expanded plasma volume, reduced heart rate, and autonomic nervous system habituation which redirects cardiac output to skin capillary beds and active muscle. Plasma volume expansion resulting from increased plasma proteins and increased sodium chloride retention, ranges from +3 to +27%, and is accompanied by a 15-25% decrease in heart rate. This reduction of cardiovascular strain reduces rating of perceived exertion, which is proportional to central cardiorespiratory stress, also decreases during the first five days of exercise-heat exposure. Plasma volume expansion is a temporary phenomenon, which decays during the 8th to 14th days of heat acclimatization (as do fluid-regulatory hormone responses, see below), and then is replaced by a longer-lasting reduction in skin blood flow that serves to increase central blood volume.
Heat acclimatization gradually disappears if not maintained by continued repeated exercise-heat exposures (Pandolf, 1998). The benefits of heat acclimatization are retained for ~1 wk and then decay with about 75% lost by ~3 wk, once heat exposure ends. During this period, re-acclimatization occurs more rapidly than the initial acclimatization when re-exposed to heat (Weller et al., 2007). A day or two of intervening cool weather will not interfere with acclimatization to hot weather. In addition, after achieving heat acclimatization, train-ing and heat acclimatization can be interspersed by every second or third day (Périard et al., 2015; Sawka et al., 2003).
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That's it for the show. Stay tuned, stay informed, and enjoy the endurance journey!