Bibliographic record
Abstract
Background and Rationale: Creatine phosphate (PCr) is degraded 𝘷𝘪𝘢 the creatine kinase (CK) enzyme to provide energy to rephosphorylate ADP back to ATP during high-intensity muscle contractions. We, and others, have previously shown that dietary creatine (Cr) loading can improve performance in short-duration, high intensity exercise in males and females. An increase in fat-free mass has also been reported, which was higher for males compared to females. It was unknown whether dietary Cr loading increases intramuscular [Cr] equally in both genders. The purpose of this investigation was to examine the effect of oral Cr loading upon [PCr] and [Cr] and exercise performance in both males and females. Methods: Twenty-seven healthy young subjects (n = 13 male, n = 14 female) participated in the investigation. Subjects performed an ischemic handgrip test, maximum voluntary contraction of dorsiflexors and knee extensors, a 30 s maximal cycling test (Wingate), and body composition (by DEXA scanning) was determined before and after supplementation with either Cr (n = 13) (5 g by mouth 4 •d⁻¹ x 5 d, followed by 5 g•d⁻¹ x 5 d) or placebo (pl; n = 14). Muscle biopsy samples were obtained before and after supplementation and were assayed for high-energy phosphates ([Cr], [PCr] and [ATP]). Results: Cr supplementation resulted in an increase in intramuscular total creatine concentration [TCr] (pl, 129.9 ± 13.8 to 132.9 ± 10.8 mMol•kg⁻¹ dw; Cr, 129.9 ± 11.6 to 146.4 ± 20.1 mMol•kg⁻¹ dw, p < 0.05) and a difference in [PCr] (pl, 72.8 ± 15.2 to 67.3 ± 4.3 mMol•kg⁻¹ dw; Cr, 70.9 ± 7.4 to 77.1 ± 13.2 mMol•kg⁻¹ dw), but had no effect on [Cr], and no differences in gender were observed. DEXA analysis showed no significant increase in total or fat-free mass; similarly, no improvements in maximum voluntary contractions were observed in either gender. In Wingate testing, males had a significant increase in peak power (pl, 971 ± 72 W to 989 ±76 W versus Cr, 994 ± 174 W to 1042 ± 154 W) and peak power per kilogram of body weight (pl, 12.8 ± 1.3 to 12.9 ± 1.1 W•kg⁻¹; Cr, 11.5 ± 1.1 to 12.1 ± 1.3 W•kg⁻¹) as a result of creatine supplementation, while females showed no significant difference. Conclusion: Creatine monohydrate supplementation at 20 g•d⁻¹ for 5 days resulted in an increase in muscle total creatine concentration for males and females, but did not affect body composition or maximum voluntary contraction. Males showed improved performance in absolute and relative peak power generation with supplementation while females did not. This may suggest that males and females respond differently to Cr supplementation.
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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) | 0.007 | 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".