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Appears in Collections:Faculty of Health Sciences and Sport Journal Articles
Peer Review Status: Refereed
Title: The effects of substrate and fluid provision on thermoregulatory, cardiorespiratory and metabolic responses to prolonged exercise in a cold environment in man
Author(s): Galloway, S D
Maughan, Ronald J
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Keywords: adult
carbohydrate intake
cardiovascular response
controlled study
dietary intake
electrolyte blood level
environmental temperature
expired air
glucose blood level
heart rate
human experiment
lung gas exchange
normal human
oxygen consumption
plasma volume
rectum temperature
respiratory function
serum osmolality
skin temperature
Issue Date: May-1998
Date Deposited: 16-Feb-2015
Citation: Galloway SD & Maughan RJ (1998) The effects of substrate and fluid provision on thermoregulatory, cardiorespiratory and metabolic responses to prolonged exercise in a cold environment in man. Experimental Physiology, 83 (3), pp. 419-430.
Abstract: During prolonged exercise in a cold environment, fatigue is generally associated with a depletion of endogenous glycogen stores. This has lead many authors to hypothesize that the carbohydrate (CHO) content of fluids ingested in cool environments should be high, yet this hypothesis has not been specifically examined. In the present study, six healthy males cycled to exhaustion at approximately 80% of their maximum oxygen consumption (V2O,max) with either no drink (ND), a 15% CHO-electrolyte drink (15% CHO) or a 2% CHO electrolyte drink (2% CHO). Dietary intake and exercise were replicated 2 days prior to each trial. Mean (S.D.) ambient temperature was 10.0 (0.3) degrees C with a relative humidity of 72 (2) % and an air velocity of approximately 0.7 m s(-1) on all trials. Weighted mean skin temperature was calculated, and rectal temperature and heart rate were recorded at rest, during exercise and at exhaustion. Venous samples were drawn before and during exercise and at exhaustion for determination of haemoglobin, haematocrit, blood metabolites and serum electrolytes and osmolality. Expired air was collected for calculation of VO2 and respiratory exchange ratio which were used to estimate rates of fuel oxidation. Ratings of perceived exertion (RPE) were also obtained. Exercise capacity was not different (P=0.49) between trials, with median (range) times to exhaustion of 90.6 (66.8-106.0), 97.7 (60.9-112.0) and 102.0 (77.1-170.7) min for the ND, 15% CHO and 2% CHO trials, respectively. The 15% CHO drink significantly (P < 0.05) elevated blood glucose concentration and total CHO oxidation compared with the ND trial. The 2% CHO drink significantly (P < 0.05) reduced the estimated change in plasma volume and resulted in a lower serum osmolality than the other two trials. No differences were observed in any thermoregulatory or cardiorespiratory responses between trials. These data suggest that maintenance of blood-borne substrate and/or plasma volume does not influence exercise capacity in the cold, as is commonly reported during this type and intensity of exercise in warmer environments.
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