Hypoperfusion At Submaximal Power Outputs In Supine Vs Upright Exercise: Contributor To Reduced VO2 Max?
Bibliographic record
Abstract
Maximal oxygen uptake (VO2max) is reduced in supine vs upright incremental cycling exercise. This could be due to a reduction only in peak oxygen delivery (O2del) with lower perfusion pressure as compensatory vasodilation preserves submaximal O2del. Alternatively, compromised O2del is already manifest during submaximal increments in power output (PO) and increases the rate of fatigue progression. PURPOSE: We tested the hypothesis that compromised O2del at submaximal power outputs increased rate of fatigue progression, reducing VO2max. METHODS: 14 untrained university aged male participants performed a step-wise incremental cycling protocol (16 Watt increments every 3 minutes) to volitional exhaustion in supine and upright. Vastus lateralis muscle oxygenation (near infrared spectroscopy), muscle activation (electromyography), gas exchange and ventilation (Moxus Metabolic Cart), venous blood lactate (finger prick) were measured. Data in mean ±SD. RESULTS: At exhaustion VO2max (ml/min/kg) peak power output (PO; Watts), venous blood lactate ([La-]v; mmol/L), Ventilation (VE; L/min) and heart rate (HR: bpm) were all decreased supine vs. upright (VO2max 35.0 ±3.7 vs. 41.7±5.7; PO 142 ±32 vs. 166 ±41; [La-]v 6.5 ±2.6 vs. 9.6 ±1.3; VE 98.6 ±17.7 vs. 127.4 ±26.8; HR 171 ±12 vs. 184 ±12, All P<0.05), but vastus lateralis oxygenated hemoglobin (O2HbVL; % peak near infrared spectroscopy signal) and muscle activity (EMG; %maximal activation) were not (O2Hb 0.27 ±0.05 vs. 0.15 ±0.10; EMG 72.6 ±24.3 vs. 88.3 ±61.2, All P>0.05). In contrast, at ventilatory threshold (Tvent) O2HbVL was reduced in supine vs. upright (0.24 ±0.21 vs. 0.44 ±0.10) while EMG was not different (P = 0.51). CONCLUSION: In supine vs. upright, reduced oxygenation at Tvent but not at exhaustion, and reduced PO, [La-]v, HR and VE at exhaustion, with no difference in EMG, is consistent with accelerated submaximal hypoperfusion-mediated fatigue compromising VO2max.
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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 | 0.000 |
| 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) | 0.003 | 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".