Feed-forward regulation of self-selected exercise intensity in response to different rates of arterial deoxygenation
Bibliographic record
Abstract
Arterial desaturation impairs exercise performance in a dose-dependent manner. However, new theories of exercise-induced fatigue suggest that increasing rates of arterial deoxygenation augment the fatigue response during exercise. The purpose of this dissertation is to clarify if self-selected exercise intensity, while exercising at a constant rate of perceived exertion (RPE), is sensitive to alterations in the absolute arterial saturation (SPO2) and/or the rate of change in SPO2. Subjects performed constant RPE exercise for 30 min. They were instructed to adjust their exercise intensity during the trial to maintain their RPE at 5 on Borg’s 10-point scale. Subjects engaged in continuous bilateral, isokinetic cycling and intermittent, unilateral, isometric knee-extension. The fraction of inspired oxygen was reduced to desaturate arterial blood from starting values (>98%) to 70%. This desaturation occurred linearly over 3 target time periods (FAST, 5 min; MED, 15 min; SLOW, 25 min). The rate of arterial desaturation was significantly different between each of the 3 conditions. During cycling exercise, PO (FAST = 2.8 ± 2.1 W·% SPO2−1; MED = 2.5 ± 1.8 W·% SPO2−1; SLOW = 1.8 ± 1.6 W·% SPO2−1; P < 0.001) and surface electromyography (sEMG) of the vastus medialis (FAST = 1.3 ± 0.6%·% SPO2−1; MED = 1.1 ± 0.5%·% SPO2−1; SLOW = 0.7 ± 0.7%·% SPO2−1; P < 0.001) decreased at significantly different rates. Post hoc comparisons revealed that the rates of decline in PO and sEMG during FAST and MED were similar, and both were greater than SLOW. However, during isometric knee extension exercise, the level of force production and sEMG remained similar across saturation levels. These results confirm that decreases in absolute SPO2 impair self-selected exercise intensity and that faster desaturation rates magnify that impairment, but only when a large muscle mass is engaged. These findings suggest that the rate of arterial deoxygenation independently influences exercise performance and that the central depressant effect may be a function of the metabolic strain associated with hypoxia, rather than the hypoxia per se.
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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".