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Fluid ingestion does not influence intense 1-h exercise performance in a mild environment
G K McConell1, T J Stephens, B J Canny
1Department of Physiology, Monash University, Clayton, Victoria, Australia. glenn.mcconell@med.monash.edu.au
Medicine and Science in Sports and Exercise
|April 3, 1999
Summary
Fluid intake during intense exercise in mild conditions offers little benefit. Hydration did not significantly impact heart rate, body temperature, or cycling performance in this study.
Area of Science:
- Exercise Physiology
- Sports Science
- Human Performance
Background:
- Standard exercise hydration guidelines aim to prevent dehydration and body mass loss.
- The efficacy of these guidelines during intense endurance exercise in mild environments remains unclear.
Purpose of the Study:
- To investigate the impact of varying fluid ingestion volumes on physiological responses and performance during intense cycling exercise in a mild environment (21°C).
Main Methods:
- Eight trained male cyclists completed a 45-minute intense cycling bout (80% VO2peak) under three conditions: no fluid (NF), 50% of body mass loss prevention volume (FR-50), and 100% of body mass loss prevention volume (FR-100).
- Following the main bout, a 15-minute all-out performance ride was conducted.
- Measurements included heart rate, rectal temperature, plasma electrolytes, body mass, and perceived exertion.
Main Results:
- Body mass loss was 1.9% in NF, 1.0% in FR-50, and 0.0% in FR-100.
- Fluid ingestion did not significantly alter heart rate, rectal temperature, plasma volume, or plasma electrolyte concentrations.
- Cycling performance during the 15-minute all-out ride was similar across all three conditions.
Conclusions:
- Ingesting water during intense, one-hour cycling exercise in mild conditions provides minimal physiological or performance benefits.
- Current hydration recommendations may not be critical for maintaining performance in this specific exercise context.