Vo2 And Leg Blood Flow Kinetics During Moderate-intensity Exercise: Effect Of Hyperventilation With And Without Added Co2
Bibliographic record
Abstract
Hyperventilation-induced hypocapnic alkalosis slows the activation of the mitochondrial pyruvate dehydrogenase complex and pulmonary O2 uptake (VO2) kinetics during the transition to moderate-intensity exercise (MOD). However, the effect of hyperventilation without the associated hypocapnic alkalosis during the transition to MOD has not been established. PURPOSE: To examine the effect of hyperventilation with and without hypocapnic alkalosis on VO2 and LBF kinetics at the onset of MOD. METHODS: Seven young male subjects (25 ± 6 yrs; mean ± SD) performed alternate-leg knee-extension exercise during a step increase in work rate from baseline (3W) to MOD (80% of estimated lactate threshold). Subjects completed 4-6 repetitions each of the following 3 conditions: i) Control (CON, PETCO2 ∼40 mmHg): Normal breathing with regular levels of CO2 (0.03%); ii) Hypocapnia (HYPO, PETCO2 ∼20 mmHg): Sustained hyperventilation with regular levels of CO2 (0.03%); and iii) Normocapnia (NORMO, PETCO2 ∼40 mmHg): Sustained hyperventilation with elevated levels of CO2 (5%). VO2 was measured breath-by-breath by mass spectrometry and volume turbine. LBF was calculated using mean blood velocity and femoral artery diameters measured by Doppler ultrasound. The adaptation of VO2 and LBF were modeled using a mono-exponential equation by non-linear regression. RESULTS: The phase 2 VO2 time constant (tVO2) was different (P < 0.05) amongst all 3 conditions: CON (19 ± 7 s), HYPO (43 ± 17 s), NORMO (30 ± 8 s); VO2 amplitude was not different amongst conditions. The adaptation of LBF (tLBF) was slower (P < 0.05) during HYPO (31 ± 9 s) compared to both CON (19 ± 3 s) and NORMO (20 ± 6 s), and the LBF amplitude was lower during HYPO (1.1 ± 0.2 L/min) compared to NORMO (1.2 ± 0.2 L/min; P = 0.049) and CON (1.2 ± 0.2 L/min; P = 0.08). CONCLUSION: While hyperventilation + hypocapnia (HYPO) was associated with slower VO2 and LBF kinetics compared to CON, preventing the fall in PETCO2 (NORMO) restored LBF kinetics but VO2 kinetics remained "slowed" relative to CON. These data suggest that some factor associated with the hyperventilation maneuver itself (i.e., independent of the induced hypocapnic alkalosis) may contribute, in part, to slowed VO2 kinetics during the transition to MOD. 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) | 0.000 | 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".