Effects of Exercise and Glucose Supplementation on Sarcoplasmic Reticulum (SR) Ca2+-handling Properties in Human Skeletal Muscle
Bibliographic record
Abstract
PURPOSE: In this study, we investigated the hypothesis that glucose supplementation will alter the functional characteristics of skeletal muscle SR Ca2+-handling proteins during prolonged exercise. METHODS: Fourteen untrained males cycled at ∼60% VO2peak on two occasions during which they were provided with either a no glucose placebo beverage (NG) or a 6% glucose (G) beverage (>1.00 g CHO per kg body mass). Beverages were provided starting after 30 min of exercise and every 15 min thereafter. SR Ca2+-handling properties (umol/g pro/min; SERCA activity; Ca2+-uptake [measured at 2uM]; Ca2+-release [20mM 4-CMC]) were assessed in homogenates prepared from tissue extracted from the vastus lateralis at rest, after 30 min and 90 min of exercise and at a time corresponding to fatigue during NG (115 ±6 min) in both NG and G, and at fatigue in G (137 ±7 min). RESULTS: Cycle time to fatigue was prolonged (p<0.05) during G compared to NG (137 ± 7 min vs. 115 ± 6 min). Plasma glucose (mM) was higher (p<0.05) at 90 min (5.8 ± 0.1 vs. 4.8 ± 0.2) and after 115 ± 6 min (5.6 ± 0.2 vs. 4.5 ±0.1) in G compared to NG, respectively. Exercise progressively reduced (p<0.05; Rest >30 min >90 min >115 ± 6 min and 137 ± 7 min) muscle pro and macro glycogen content in both conditions. Although exercise progressively reduced pro and macro glycogen content, no differences in glycogen content were observed at matched time points between NG and G (i.e.; 90 min, 115 ± 6 min, and 137 ± 7 min). No differences in resting SR properties (SERCA Vmax, 174 ±7 vs. 177 ± 10; Ca2+-uptake, 6.4 ± 0.3 vs 6.3 ±0.4; Phase 1 Ca2+-release, 23.4 ± 1.3 vs 23.0 ± 1.1; Phase 2 Ca2+-release, 7.3 ± 0.4 vs 7.3 ± 0.5) were observed between NG and G, respectively. Prolonged exercise reduced (p<0.05; main effect; Rest >30 min and 90 min >115 ±6 min, and 137 ±7 min) SERCA Vmax during both the G and NG conditions. During the NG ride, Vmax was depressed by 10.9 and 18.2% after 90 min of exercise and after 115 ± 6 min, respectively. During the G ride, SERCA Vmax was depressed by 7.4, 12.4 and 17.5% after 90 min, 115 ± 6 min and 137 ± 7 min, respectively. Similar exercise-induced reductions (p<0.05) were also observed for SR Ca2+-uptake and SR Ca2+-release (Phase 1 and Phase 2) kinetics during NG and G. Although exercise progressively reduced SR Ca2+-handling properties, no differences were observed at matched time points between NG and G (i.e.; 90 min, 115 ± 6 min, and 137 ± 7 min) for any SR Ca2+-handling property assessed. CONCLUSIONS: These results indicate the increase in exercise ride time during G, compared to NG, can not be explained by differences in SR Ca2+-handling properties during exercise. Funded by the Gatorade Sports Science Institute.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 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 teacher head, 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".