The effects of water ingestion on high intensity cycling performance in a moderate ambient temperature

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dc.contributor.advisorHawley, Johnen_ZA
dc.contributor.advisorDennis, Steveen_ZA
dc.contributor.authorRobinson, Tracy Anneen_ZA
dc.date.accessioned2018-01-29T06:46:25Z
dc.date.available2018-01-29T06:46:25Z
dc.date.issued1994en_ZA
dc.description.abstractEight endurance~trained cyclists rode as far as possible in 1 h on a stationary cyclesimulator in a moderate environment (20°C, 60% relative humidity, 3 m/s wind speed) while randomly receiving either no fluid (NF) or attempting to replace their ~1.7 l sweat loss measured in a previous 1 h familiarisation performance ride at ~85% of peak oxygen uptake (VO₂ peak) with artificially sweetened, coloured water (F). During F the cyclists drank 1.49 ± 0.14 1 (values are mean± SEM), of which 0.27 ± 0.08 1 remained in the stomach at the end of exercise and 0.20 ± 0.05 1 was urinated after the trial. Thus, only 1.02 ± 0.12 l of the ingested fluid was available to replace sweat losses during the 1 h performance ride. That fluid decreased the average heart rate from 166 ± 3 to 157 ± 5 beats/min (P < 0.0001) and reduced the final serum [Na+] and osmolalities from 143 ± 0.6 to 139 ± 0.6 mEq/1 (P < 0.005) and from 294 ± 1.7 to 290 ± 1.9 mOsm/1 (P = 0.05), respectively. Fluid ingestion did not attenuate rises in plasma anti diuretic hormone and angiotensin concentrations, or decrease the ~-15% falls in estimated plasma volume in the F and NF trials. Nor did fluid ingestion significantly effect the ~1.7 l/h sweat rates, the rises in rectal temperature (~36.6° to 38.3°C) or the ratings of perceived exertion in the two trials. Ingestion of ~1.5 l of fluid produced an uncomfortable stomach fullness and reduced the distance covered in 1 h from 43.1 ± 0. 7 to 42.3 ± 0.6 km (P<0.05). Thus, trying to replace > 1.0 l/h sweat losses during high-intensity, short duration exercise in a moderate environment does not induce beneficial physiological effects, and may impair exercise performance.en_ZA
dc.identifier.apacitationRobinson, T. A. (1994). <i>The effects of water ingestion on high intensity cycling performance in a moderate ambient temperature</i>. (Thesis). University of Cape Town ,Faculty of Health Sciences ,MRC/UCT RU for Exercise and Sport Medicine. Retrieved from http://hdl.handle.net/11427/27033en_ZA
dc.identifier.chicagocitationRobinson, Tracy Anne. <i>"The effects of water ingestion on high intensity cycling performance in a moderate ambient temperature."</i> Thesis., University of Cape Town ,Faculty of Health Sciences ,MRC/UCT RU for Exercise and Sport Medicine, 1994. http://hdl.handle.net/11427/27033en_ZA
dc.identifier.citationRobinson, T. 1994. The effects of water ingestion on high intensity cycling performance in a moderate ambient temperature. University of Cape Town.en_ZA
dc.identifier.ris TY - Thesis / Dissertation AU - Robinson, Tracy Anne AB - Eight endurance~trained cyclists rode as far as possible in 1 h on a stationary cyclesimulator in a moderate environment (20°C, 60% relative humidity, 3 m/s wind speed) while randomly receiving either no fluid (NF) or attempting to replace their ~1.7 l sweat loss measured in a previous 1 h familiarisation performance ride at ~85% of peak oxygen uptake (VO₂ peak) with artificially sweetened, coloured water (F). During F the cyclists drank 1.49 ± 0.14 1 (values are mean± SEM), of which 0.27 ± 0.08 1 remained in the stomach at the end of exercise and 0.20 ± 0.05 1 was urinated after the trial. Thus, only 1.02 ± 0.12 l of the ingested fluid was available to replace sweat losses during the 1 h performance ride. That fluid decreased the average heart rate from 166 ± 3 to 157 ± 5 beats/min (P < 0.0001) and reduced the final serum [Na+] and osmolalities from 143 ± 0.6 to 139 ± 0.6 mEq/1 (P < 0.005) and from 294 ± 1.7 to 290 ± 1.9 mOsm/1 (P = 0.05), respectively. Fluid ingestion did not attenuate rises in plasma anti diuretic hormone and angiotensin concentrations, or decrease the ~-15% falls in estimated plasma volume in the F and NF trials. Nor did fluid ingestion significantly effect the ~1.7 l/h sweat rates, the rises in rectal temperature (~36.6° to 38.3°C) or the ratings of perceived exertion in the two trials. Ingestion of ~1.5 l of fluid produced an uncomfortable stomach fullness and reduced the distance covered in 1 h from 43.1 ± 0. 7 to 42.3 ± 0.6 km (P<0.05). Thus, trying to replace > 1.0 l/h sweat losses during high-intensity, short duration exercise in a moderate environment does not induce beneficial physiological effects, and may impair exercise performance. DA - 1994 DB - OpenUCT DP - University of Cape Town LK - https://open.uct.ac.za PB - University of Cape Town PY - 1994 T1 - The effects of water ingestion on high intensity cycling performance in a moderate ambient temperature TI - The effects of water ingestion on high intensity cycling performance in a moderate ambient temperature UR - http://hdl.handle.net/11427/27033 ER - en_ZA
dc.identifier.urihttp://hdl.handle.net/11427/27033
dc.identifier.vancouvercitationRobinson TA. The effects of water ingestion on high intensity cycling performance in a moderate ambient temperature. [Thesis]. University of Cape Town ,Faculty of Health Sciences ,MRC/UCT RU for Exercise and Sport Medicine, 1994 [cited yyyy month dd]. Available from: http://hdl.handle.net/11427/27033en_ZA
dc.language.isoengen_ZA
dc.publisher.departmentMRC/UCT RU for Exercise and Sport Medicineen_ZA
dc.publisher.facultyFaculty of Health Sciencesen_ZA
dc.publisher.institutionUniversity of Cape Town
dc.subject.otherSports Medicineen_ZA
dc.subject.otherCyclingen_ZA
dc.subject.otherDehydrationen_ZA
dc.subject.otherExertion - physiologyen_ZA
dc.subject.otherDrinking (Physiology)en_ZA
dc.titleThe effects of water ingestion on high intensity cycling performance in a moderate ambient temperatureen_ZA
dc.typeMaster Thesis
dc.type.qualificationlevelMasters
dc.type.qualificationnameMPhilen_ZA
uct.type.filetypeText
uct.type.filetypeImage
uct.type.publicationResearchen_ZA
uct.type.resourceThesisen_ZA
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