Core temperature and hydration status during an Ironman triathlon * Commentary * Commentary
- 1 April 2006
- journal article
- research article
- Published by BMJ in British Journal of Sports Medicine
- Vol. 40 (4), 320-325
- https://doi.org/10.1136/bjsm.2005.022426
Abstract
Numerous laboratory based studies have documented that aggressive hydration strategies (approximately 1-2 litres/h) are required to minimise a rise in core temperature and minimise the deleterious effects of hyperthermia on performance. However, field data on the relations between hydration level, core body temperature, and performance are rare. To measure core temperature (Tcore) in triathletes during a 226 km Ironman triathlon, and to compare Tcore with markers of hydration status after the event. Before and immediately after the 2004 Ironman Western Australia event (mean (SD) ambient temperature 23.3 (1.9) degrees C (range 19-26 degrees C) and 60 (14)% relative humidity (44-87%)) body mass, plasma concentrations of sodium ([Na+]), potassium ([K+]), and chloride ([Cl-]), and urine specific gravity were measured in 10 well trained triathletes. Tcore was measured intermittently during the event using an ingestible pill telemetry system, and heart rate was measured throughout. Mean (SD) performance time in the Ironman triathlon was 611 (49) minutes; heart rate was 143 (9) beats/min (83 (6)% of maximum) and Tcore was 38.1 (0.3) degrees C. Body mass significantly declined during the race by 2.3 (1.2) kg (-3.0 (1.5)%; p < 0.05), whereas urine specific gravity significantly increased (1.011 (0.005) to 1.0170 (0.008) g/ml; p < 0.05) and plasma [Na+], [K+], and [Cl-] did not change. Changes in body mass were not related to finishing Tcore (r = -0.16), plasma [Na+] (r = 0.31), or urine specific gravity (r = -0.37). In contrast with previous laboratory based studies examining the influence of hypohydration on performance, a body mass loss of up to 3% was found to be tolerated by well trained triathletes during an Ironman competition in warm conditions without any evidence of thermoregulatory failure.Keywords
This publication has 26 references indexed in Scilit:
- Relationship between laboratory-measured variables and heart rate during an ultra-endurance triathlonJournal of Sports Sciences, 2005
- The effects of different air velocities on heat storage and body temperature in humans cycling in a hot, humid environmentActa Physiologica Scandinavica, 2005
- Sodium ingestion and the prevention of hyponatraemia during exerciseBritish Journal of Sports Medicine, 2004
- Fluid Replacement during Marathon RunningClinical Journal of Sport Medicine, 2003
- Overconsumption of fluids by athletesBMJ, 2003
- Nutrition and Athletic PerformanceMedicine & Science in Sports & Exercise, 2000
- Hydration Effects on Temperature RegulationInternational Journal of Sports Medicine, 1998
- Effects of Training, Environment, and Host Factors on the Sweating Response to ExerciseInternational Journal of Sports Medicine, 1998
- ACSM Position Stand: Exercise and Fluid ReplacementMedicine & Science in Sports & Exercise, 1996
- Variation in Total Body Water with Muscle Glycogen Changes in ManActa Physiologica Scandinavica, 1970