The Adjustments of Δ[HHb] and VO2p During Ramp Incremental Exercise in Young and Older Adults
Bibliographic record
Abstract
The matching of muscle O2 delivery to O2 utilization can be inferred from the adjustments in muscle deoxygenation ([HHb], reflecting fractional O2 extraction) and pulmonary O2 uptake (VO2p). Although the adjustments of Δ[HHb] and in healthy young (YA) and older (OA) adults have been analyzed previously during step-transitions to constant- load, moderate exercise, comparisons during non-steady-state ramp incremental (RI) exercise, where work rates (WR) span across light-to-very heavy intensity exercise domains, have not been made. PURPOSE: To examine the adjustments of [HHb] and VO2p during RI exercise in healthy YA and OA. METHODS: Ten YA (25 ± 5 yrs; mean ± SD) and nine OA (70 ± 3 yrs; mean ± SD) completed 2 RI exercise tests (20 W/min) from a baseline of 20 W to volitional fatigue. VO2p was measured breath-by-breath using a volume turbine and a mass spectrometer, and muscle deoxygenation (Δ[HHb]) of the vastus lateralis muscle was measured using near-infrared spectroscopy. All data were time-aligned and time-averaged into 5 s bins to yield a single, averaged response profile. VO2p response profiles, as a function of absolute WR, were modelled using linear regression analysis. Δ[HHb] response profiles were normalized from baseline (0%) to peak Δ[HHb] (100%) and fit using a sigmoid model as a function of i) absolute WR (W) and ii) relative WR (% of peak WR). RESULTS: YA displayed a greater relative peak VO2p (49 ± 5 mL·kg-1·min-1) compared to the OA (30 ± 6 mL·kg-1·min-1). Slopes of the VO2p-WR relationship were found to be similar (P > 0.05) in YA (9.9 ±.4 mL·min-1·W-1) and OA (9.2 ±.9 mL·min-1·W-1). The sigmoid slope (d) of the Δ[HHb]-WR relationship was greater (P < 0.05) in OA (0.027 ± 0.01 % W-1) compared to YA (0.017 ± 0.01 % W-1), and the c/d value (WR corresponding to 50 % of the sigmoid amplitude) was smaller (P < 0.05) for OA (133 ± 40 W) than in YA (195 ± 51 W). No age-related differences were found for any of the sigmoid parameters when the relationship was expressed as a % of peak WR. CONCLUSION: During RI exercise, for any given WR (or VO2p) OA displayed a greater reliance on muscle O2 extraction, suggesting a lower muscle O2 delivery-to-O2 utilization relationship throughout a range of exercise intensities. Supported by: NSERC
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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".