Sweat Loss, Fluid Intake and Sodium Balance in Triathletes During a 1 hr Cycling Test
Bibliographic record
Abstract
Previous research shows that losing ∼2% of body mass (BM) through sweating results in impaired athletic performance. Endurance athletes can easily lose ∼2% of BM in as little as 1 - 2 hr during moderate intensity cycling (60 - 65 % VO2max). PURPOSE: To examine the pre-exercise hydration status and exercise sweat rate, fluid intake and sweat sodium losses of Olympic distance and full Ironman triathletes (n = 23, 31.3 ± 1.9 years, 69.5 ± 1.7 kg, 1.76 ± 0.02 m) during 1 hr of cycling at self-selected "race pace" (226 ± 10 W) in temperate conditions (22.4 ± 0.2 °C, 49.4 ± 3.7 % relative humidity). METHODS: Subjects were asked to prepare for the testing as they would for a typical competition. They provided a urine sample for the estimation of pre-exercise hydration status, and were weighed pre- and post-exercise. Fluid intake was monitored during the ride and sweat sodium was measured in forehead, forearm and back sweat patches. Athletes drank their preferred fluid ad libitum and consumed gels in some cases. RESULTS: Urine specific gravity was 1.013 ± 0.002 and only 6/23 subjects were classified as dehydrated (USG > 1.020) before exercising. The triathletes lost 1.5 ± 0.1 L of sweat during the hour cycle and drank 983 ± 98 mL of fluid. Fifteen out of 23 subjects consumed a sports drink and the average intake was 514 ± 116 mL. Mean BM loss was 0.8 ± 0.2 % and no subject lost > 2% BM. Only 4/23 subjects lost between 1.5 - 2% BM at the end of the hour. Mean forehead, forearm and back sweat sodium concentrations were 81 ± 6, 64 ± 6, and 76 ± 4 mM, respectively. Total sodium loss was 2.7 ± 0.3 g and total sodium intake was 0.3 ± 0.1 g. Total carbohydrate intake averaged 40 ± 7 g. CONCLUSION: Under "simulated" race conditions, triathletes drank enough fluid to successfully minimize their BM losses for one hour of exercise. However, they replaced only ∼10% of the sodium lost in sweat, and ingested a moderate amount of carbohydrate. With an Olympic distance triathlon lasting ∼2 hr and a full Ironman lasting ∼9 + hr, these athletes need to be aware that the fluid and sodium losses they experience are cumulative and should increase their fluid, carbohydrate and sodium intake accordingly with race duration to avoid decreases in athletic performance. Supported by GSSI Canada.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 0.001 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".