ABSTRACT
The purpose of this study was to investigate thermal response, hydration and performance over a 6-day, 142-km trail running race in tropical conditions. 9 participants competed in the 2011 Gwadarun (30°C±2.4 °C and 82±4% RH). Data were collected on days 1, 4 and 6. Gastrointestinal temperature (Tgi) and heart rate (HR) were measured using portable telemetry units, whereas blood samples were collected for hematocrit, osmolarity, plasma concentrations, alkaline reserves and creatine phosphokinase. The performances expressed in speed were correlated with both total body water and body mass loss per hour (TBWL.h(-1) and ∆BM.h(-1)), HR and changes in Tgi per hour (∆Tgi.h(-1)): the more water and mass the participants lost, the higher the HR and the greater the Tgi change, and the better the performance. The ∆ Tgi.h(-1) was significantly correlated with ∆BM.h(-1), and the participants who lost the most mass had the greatest increases in Tgi. None of the blood parameters demonstrated significant changes. The present study showed that well-trained acclimated runners performing a 6-day trail race in a tropical environment and drinking ad libitum did not demonstrate heat-related illness or severe dehydration. Moreover, high performance was associated with increases in Tgi, TBW and BM losses per hour.
Subject(s)
Athletic Performance/physiology , Body Temperature Regulation/physiology , Drinking , Running/physiology , Tropical Climate , Adaptation, Physiological , Adult , Body Mass Index , Body Temperature , Body Water/physiology , Dehydration/physiopathology , Female , Gastrointestinal Tract/physiology , Heart Rate/physiology , Humans , Male , Middle AgedABSTRACT
We evaluated the effects of the fluid replacement strategy on core temperature, heart rate and urine osmolality during a 27-km trail run in tropical climate. 20 well-trained runners completed a 27-km trail race in tropical conditions. They were acclimatized to these conditions. Heart rate was monitored every 5 s, while core temperature and perceived thermal and comfort sensations were recorded before, at the 11(th) km, and just after the end of the race. Water intake, urine osmolality and body mass were measured before and after the race. Core temperature and the scores of perceived thermal and comfort sensations were significantly higher at the 11(th) km and at the end of the race compared to before the race, but not at the 11(th) km compared to the end of the race [corrected]. No participant exhibited dehydration as assessed by urine osmolality. The less the trail runners weighed, the greater the heat retention was. The less hot they felt at the end of the race, the more they lost water, and the better the performance was. The fastest runners were able to tolerate a greater variation in core temperature between the beginning and the end of the trail race with lower water intake.
