The Effects Of Hypohydration On Exercise Skeletal Muscle Metabolism In Males
Bibliographic record
Abstract
Previous research has demonstrated that sweat losses of as little as 2% body mass (BM) may compromise athletic performance. However there is little data investigating the impact of mild hypohydration on skeletal muscle metabolism during exercise. PURPOSE: This study investigated the metabolic responses to 120 min of cycling as subjects became progressively hypohydrated (HYPO) or maintained BM by replacing sweat losses (HYD). We hypothesized that whole body carbohydrate oxidation and muscle glycogen use would be greater in the final 40 min of exercise in the HYPO trial when hypohydration was the largest. METHODS: Nine active males participated in the study (21.6 ± 0.5 yr, 77.3 ± 2.2 kg, 56.9 ± 2.3 ml/kg/min). Subjects cycled at ∼ 67 % VO2peak (23°C, 33% RH) with blood samples taken at rest and every 20 min and muscle biopsies taken at 0, 40, 80, and 120 min. RESULTS: Based on USG, subjects were hydrated prior to each trial (HYPO 1.015 ± 0.003 vs. HYD 1.013 ± 0.003). Subjects lost 0.8% BM after 40 min, 1.8% BM after 80 min, and 2.7% BM after 120 min of cycling in the HYPO trial. Mean RER over the 120 min was the same for both trials (HYPO 0.91 ± 0.02 vs. HYD 0.91 ± 0.01) and there was no difference in RER from 0-40 (0.93 ± 0.1 vs. 0.93 ± 0.2), 40-80 (0.90 ± 0.2 vs. 0.90), or 80-120 min (0.87 ± 0.01 vs. 0.88 ± 0.01) between trials. Blood [La] was significantly higher in the HYPO trial from 20 min onward. Blood glucose and plasma free fatty acids were not significantly different between trials. Muscle PCr and ATP significantly changed in both trials with no significant effect of trial. There was no significant difference in muscle glycogen use between trials between 0-40, 40-80, or 80-120 min (HYPO 244 ± 42, 80 ± 19, 93 ± 25, vs. HYD 215 ± 30, 87 ± 14, 63 ± 12 mmol/kg dm). Muscle [La] was significantly higher at 120 min in the HYPO trial (9.9 ± 2.8 vs. HYD 5.7 ± 1.4 mmol/kg dm). CONCLUSION: In the final 40 min of the 2 hour cycle in the HYPO trial, subjects were between 1.8 and 2.7% hypohydrated. However, contrary to our hypotheses, whole body carbohydrate oxidation and skeletal muscle glycogen use (∼50% increase in HYPO, but not significant) were not significantly affected by mild hypohydration. Supported by NSERC and GSSI Canada.
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
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) | 0.001 | 0.000 |
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".