Effects of Combined Creatine and Glycerol Supplementation on Physiological Responses During Exercise in the Heat
Bibliographic record
Abstract
It is well documented that exercising in high ambient temperature environments can have a profound effect on thermoregulation and exercise performance. Both glycerol (Gly) and creatine (Cr) have been shown to act as hyperhydrating agents when consumed with fluid and to reduce thermal strain during prolonged exercise in the heat (e.g. Lyons et al. Med Sci Sports Exerc 22: 77–83, 1990; Kilduff et al. Int J Sport Nutr Exerc Metab 14: 443–60, 2004). PURPOSE: To examine the effects of combined Cr and Gly supplementation, intended to increase initial total body water (TBW) levels, on the physiological responses to prolonged exercise in the heat. METHODS: Twenty-three well-trained male cyclists were matched for body mass (BM) and were randomised in a double blind fashion to either a Cr or a placebo (Pl) group. Cr supplementation consisted of 22.8 g·d−1 of Cr·H2O (equivalent to 10 g Cr × 2 daily) and 75 g of glucose polymer made up in 1 litre (L) of warm water (x 2 daily). The Pl supplement consisted of 170 g·d−1 of glucose polymer (85 g × 2 daily). Subjects participated in two supplementation regimens each lasting seven days and comprising an exercise trial both pre- and post-supplementation. During the first supplementation regimen, subjects in both groups received either 1 g Gly·kg−1 BM or an equivalent amount of Pl before crossing over during the second supplementation regimen. The exercise trials consisted of 40 min constant-load exercise at 63% WRmax followed by a 16.1 km (10 mile) time trial at 30° C ambient temperature and 70% relative humidity. RESULTS: In the Pl group, TBW increased (mean ± s.d.) by 0.57 ± 0.27 L (p<0.01) during Gly supplementation and did not change significantly during supplementation with Pl (P=0.52). In the Cr group, TBW increased by 0.63 ± 0.33 L (p<0.01) during Pl and by 0.87 ± 0.21 L (p<0.01) during Gly supplementation. The rise in heart rate (HR), rectal temperature (Tre) and rating of perceived exertion (RPE) during exercise was significantly attenuated after both supplementation regimens in the Cr group. However, there was no difference in pre and post supplementation time trial performance in either group. The addition of Gly to Cr significantly increased TBW further than Cr alone (P=0.02) but did not further enhance the attenuation in HR, Tre and RPE during exercise. CONCLUSIONS: The combination of Cr and Gly is more effective at hyperhydrating than either Cr or Gly alone but does not further enhance the reduction in thermal strain compared to Cr alone. The possibility that this novel “water-loading” protocol may improve performance during exercise of greater duration in the heat remains to be determined. Supported by Iovate Health Sciences Research Inc, 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 | 0.001 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 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 | 0.001 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.002 | 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".