Na+-K+-ATPase Responses During Prolonged Cycle Exercise to Fatigue in Response to Dietary Carbohydrate (CHO) Manipulation
Bibliographic record
Abstract
PURPOSE: In this study, we investigated the effects of prolonged exercise on muscle Na+-K+-ATPase function in males following dietary CHO manipulation. METHODS: Seven healthy male volunteers (VO2peak = 39.2 ± 1.8 mL/kg/min) cycled at ∼65% of their peak aerobic power (VO2peak) on two occasions; namely following a 4-day high CHO diet (Hi CHO) and following a 4-day low CHO diet (Lo CHO). A glycogen depletion protocol was completed prior to each condition. Muscle samples from the vastus lateralis were collected at rest, 30 min of exercise, Lo CHO fatigue, and Hi CHO fatigue. Maximal Na+-K+-ATPase activity (Vmax) was assessed using the 3-O-methylfluorescein phosphatase assay while the maximal number of alpha subunits (βmax) was measured using the [3H] ouabain binding technique. RESULTS: In Lo CHO, Vmax (nmole/mg protein/h) was reduced (p<.05) at 30 min (71 ± 3) but not at Lo CHO fatigue (80 ± 10) compared to rest (87 ± 6). A similar pattern was observed for Hi CHO, namely a reduction (p<.05) at 30 min (70 ± 7) and no change at Lo CHO fatigue (94 ± 6) compared to rest (88 ± 14). No further change was found at Hi CHO fatigue (104 ± 7). Although no differences in Vmax were observed between Lo CHO and Hi CHO at similar time points, Vmax was higher (p<.05) at fatigue in Hi CHO compared to Lo CHO. Time to fatigue in Hi CHO (103 ± 9.3 min) increased by 54% compared to Lo CHO (66.7 ± 5.9 min). Increases (p<.05) in βmax (pmol/g) from rest to fatigue were observed in Lo CHO (291 ± 15 vs. 316 ± 19) and Hi CHO (311 ± 21 vs. 336 ± 9). There was a trend (p=.07) for βmax to be higher in Hi CHO compared to Lo CHO. Total muscle glycogen (mmol glucosyl units/kg dry wt) was higher (P < 0.05) in Hi CHO compared with Lo CHO at rest (+36%), at 30 min (+53%), and at Lo CHO fatigue (+44%). CONCLUSIONS: These changes in Vmax with exercise suggest that 2 mechanisms are involved, one that depresses Vmax early in exercise and one that restores Vmax as exercise progresses. Manipulation of muscle glycogen levels did not alter the response. The increase in α subunit abundance observed at fatigue suggests a translocation to the sarcolemma, an effect which may be potentiated by Hi CHO. Supported by NSERC (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".