Protein-carbohydrate Ingestion Does Not Alter Selected Markers Of Skeletal Muscle Metabolism During Exercise In Trained Cyclists
Bibliographic record
Abstract
Ingesting protein (PRO) with carbohydrate (CHO) during prolonged exercise is purported to alter the acute metabolic response of skeletal muscle compared to CHO alone, however no study has directly investigated this issue. PURPOSE: We tested the hypothesis that, as compared to CHO alone, ingesting CHO+PRO would alter selected markers of metabolic control during exercise, including the magnitude of glycogen and phosphocreatine (PCr) utilization, muscle lactate accumulation and net expansion of the tricarboxylic acid cycle intermediate (TCAI) pool. METHODS: Eight trained male cyclists (29±2 y; VO2peak = 55±2 ml/kg/min) performed a 90 min ride (Ride 1) at 65% of VO2peak on three occasions and needle biopsy samples (v. lateralis) were obtained before and after exercise. In a randomized, double-blind manner, subjects ingested one of three drinks during exercise that contained either 6% CHO + 2% PRO, 6% CHO or a non-energetic placebo (PLA) at a rate of 1 L/h. Following Ride 1, diet was strictly controlled for 24 h before subjects performed a 500 kJ cycling time trial (Ride 2). RESULTS: There was no difference between trials in muscle glycogen utilization DURING exercise (CHO: 465±20 > 283±43; CHO+PRO: 472±45 > 244±33; PLA: 572± 51 > 280±56 mmol/kg dry wt.; main effect for time, P<0.05). Similarly, muscle PCr utilization, lactate accumulation and the increase in the TCAI citrate and malate during exercise was not different between trials (all main effects, P<0.05). Venous blood creatine kinase activity, a marker of sarcolemmal disruption, was elevated immediately prior to Ride 2 compared to pre-Ride 1 (main effect, P<0.05) but there was no difference between treatments. Time trial performance in Ride 2 was not different between trials (CHO: 32.1±1.0; CHO+PRO: 32.1±1.0; PLA: 32.2±1.1 min). CONCLUSION: Ingesting CHO+PRO during exercise did not alter selected markers of skeletal muscle metabolic control compared to CHO alone. Skeletal muscle mechanisms purported to explain the potential ergogenic benefit of CHO+PRO ingestion during exercise remain speculative. Supported by NSERC, 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 | 0.001 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.001 | 0.001 |
| 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".