Oxygen Extraction Reserve Immediately After Ramp Incremental Maximal Exercise
Bibliographic record
Abstract
Towards the end of a ramp incremental (RI) test to exhaustion, the near-infrared spectroscopy (NIRS)-derive deoxygenated hemoglobin ([HHb]) signal plateaus, suggesting an upper limit in oxygen (O2) extraction. However, it is unknown whether this plateau is the highest level of O2 extraction, or if a “reserve” in O2 extraction exists, such that the plateau in the [HHb] in the presence of a still raising O2 utilization (VO2) towards the end of a RI test is indicative of a local increase in blood flow. PURPOSE: To assess the existence of a “reserve” in O2 extraction immediately at the end of a RI cycling test to exhaustion. METHODS: Nine male participants (27 ± 4.6 yrs; 79.9 ± 8.6 kg) performed a RI (30W[BULLET OPERATOR]min -1) test to exhaustion on a cycle ergometer (Velotron Dynafit Pro, Seattle, WA, USA) to determine the VO2 (Quark CPET, Cosmed, Rome, Italy) and the [HHb] (Oxiplex TS, ISS, Champaign, USA) responses. The [HHb] signal was measured on the Vastus Lateralis (VL) muscle. An automatic rapid inflation cuff was used to occlude blood flow to the leg (300 mmHg), at the upper portion of the thigh, for two minutes immediately at test failure. A paired samples t-test was used to compare the VO2 (onset of the plateau in the [HHb] signal and end-exercise) and the normalized (0-100% of the response during RI test) [HHb] signal (plateau and peak value obtained during occlusion). RESULTS: The end-exercise VO2 (VO2max; 4.35 ± 0.57 L[BULLET OPERATOR]min-1) was larger than that observed at the onset of the plateau in the [HHb] response (3.77 ± 0.52 L[BULLET OPERATOR]min-1; p <0.05). Post-exercise peak [HHb] (following occlusion) was higher compared to its plateau value (p <0.05), with a mean difference of 38.1 ± 18.9 %. CONCLUSIONS: This study demonstrated the existence of a “reserve’ in O2 extraction, despite a continuous increase in the VO2 response towards the end of a RI cycling test. These data suggest that the observed plateau in the [HHb] response is not related to O2 extraction reaching its upper limit, but likely due to increased local blood flow.
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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) | 0.002 | 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".