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Impaired high-intensity cycling performance time at low levels of dehydration.
Int J Sports Med. 1994 Oct; 15(7):392-8.IJ

Abstract

On two separate occasions six trained subjects (peak oxygen consumption [VO2peak] 4.41/min) rode for 60 min at 70% of VO2peak and then to exhaustion at 90% of VO2peak to determine the effects of mild dehydration on high-intensity cycling performance time in the heat (32 degrees C, 60% relative humidity, wind speed 3 km/h). In one trial (F) subjects ingested a 400 ml bolus of 20 mmol/l NaCl immediately before, and then as repetitive 120 ml feedings every 10 min during the first 50 min of exercise. In the other trial they did not ingest fluid (NF) either before or during exercise. The order of testing was in a counter-balanced random sequence. For the first 60 min of exercise mean (+/- SD) VO2 (2.90 +/- 0.39 vs 2.93 +/- 0.38 l/min) and respiratory exchange ratio (RER; 0.95 +/- 0.03 vs 0.94 +/- 0.04) values were similar between F and NF trials. However, weight loss was significantly reduced during F compared to NF (0.16 +/- 0.39 vs 1.30 +/- 0.22 kg; p < 0.005) and high-intensity cycling time to exhaustion was significantly increased (9.8 +/- 3.9 vs 6.8 +/- 3.0 min; p < 0.005). Increased cycling times to exhaustion in the F trial were not associated with any measurable differences in heart rate (HR), body temperature, respiratory gas exchange, leg muscle power over 5 sec, or the degree to which fluid ingestion reduced the level of dehydration within the group. Only the ratings of perceived exertion (RPE) and plasma anti diuretic hormone (ADH) concentrations were significantly increased in the NF trial compared to the F trial.(

ABSTRACT

TRUNCATED AT 250 WORDS)

Authors+Show Affiliations

Medical Research Council/University of Cape Town Medical School, Department of Physiology, Observatory, South Africa.No affiliation info availableNo affiliation info availableNo affiliation info available

Pub Type(s)

Clinical Trial
Journal Article
Randomized Controlled Trial
Research Support, Non-U.S. Gov't

Language

eng

PubMed ID

8002117

Citation

Walsh, R M., et al. "Impaired High-intensity Cycling Performance Time at Low Levels of Dehydration." International Journal of Sports Medicine, vol. 15, no. 7, 1994, pp. 392-8.
Walsh RM, Noakes TD, Hawley JA, et al. Impaired high-intensity cycling performance time at low levels of dehydration. Int J Sports Med. 1994;15(7):392-8.
Walsh, R. M., Noakes, T. D., Hawley, J. A., & Dennis, S. C. (1994). Impaired high-intensity cycling performance time at low levels of dehydration. International Journal of Sports Medicine, 15(7), 392-8.
Walsh RM, et al. Impaired High-intensity Cycling Performance Time at Low Levels of Dehydration. Int J Sports Med. 1994;15(7):392-8. PubMed PMID: 8002117.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Impaired high-intensity cycling performance time at low levels of dehydration. AU - Walsh,R M, AU - Noakes,T D, AU - Hawley,J A, AU - Dennis,S C, PY - 1994/10/1/pubmed PY - 1994/10/1/medline PY - 1994/10/1/entrez SP - 392 EP - 8 JF - International journal of sports medicine JO - Int J Sports Med VL - 15 IS - 7 N2 - On two separate occasions six trained subjects (peak oxygen consumption [VO2peak] 4.41/min) rode for 60 min at 70% of VO2peak and then to exhaustion at 90% of VO2peak to determine the effects of mild dehydration on high-intensity cycling performance time in the heat (32 degrees C, 60% relative humidity, wind speed 3 km/h). In one trial (F) subjects ingested a 400 ml bolus of 20 mmol/l NaCl immediately before, and then as repetitive 120 ml feedings every 10 min during the first 50 min of exercise. In the other trial they did not ingest fluid (NF) either before or during exercise. The order of testing was in a counter-balanced random sequence. For the first 60 min of exercise mean (+/- SD) VO2 (2.90 +/- 0.39 vs 2.93 +/- 0.38 l/min) and respiratory exchange ratio (RER; 0.95 +/- 0.03 vs 0.94 +/- 0.04) values were similar between F and NF trials. However, weight loss was significantly reduced during F compared to NF (0.16 +/- 0.39 vs 1.30 +/- 0.22 kg; p < 0.005) and high-intensity cycling time to exhaustion was significantly increased (9.8 +/- 3.9 vs 6.8 +/- 3.0 min; p < 0.005). Increased cycling times to exhaustion in the F trial were not associated with any measurable differences in heart rate (HR), body temperature, respiratory gas exchange, leg muscle power over 5 sec, or the degree to which fluid ingestion reduced the level of dehydration within the group. Only the ratings of perceived exertion (RPE) and plasma anti diuretic hormone (ADH) concentrations were significantly increased in the NF trial compared to the F trial.(ABSTRACT TRUNCATED AT 250 WORDS) SN - 0172-4622 UR - https://www.unboundmedicine.com/medline/citation/8002117/Impaired_high_intensity_cycling_performance_time_at_low_levels_of_dehydration_ L2 - http://www.thieme-connect.com/DOI/DOI?10.1055/s-2007-1021076 DB - PRIME DP - Unbound Medicine ER -