Does Improved Local O2 Distribution Explain Faster VO2 Kinetics During Smaller Compared To Larger Moderate-intensity Transitions?
Bibliographic record
Abstract
Moderate-intensity exercise (MOD) transitions of different amplitudes yield differing pulmonary O2 uptake profiles (VO2p kinetics) even within an individual; yet, the precise mechanism(s) responsible for regulating VO2p kinetics remain elusive. Insights into the balance between local muscle O2 delivery and O2 utilization (VO2m) can be gleaned from the ratio of NIRS-derived muscle deoxygenation (Δ[HHb])-to-VO2m (represented by phase II VO2p) to determine whether O2 delivery may constrain VO2p kinetics. PURPOSE: To compare the VO2p and Δ[HHb] responses to two discrete MOD step increases in work rate (WR). METHODS: Six healthy, young males each completed 4 repetitions of leg cycling MODs in 2 protocols which included 6min of cycling at 20W followed by 6min at either 90W (MOD90) or 130W (MOD130). VO2p and Δ[HHb] responses were modeled as a mono-exponential using non-linear regression, and later scaled to a relative % of the respective response (0-100%). The transient Δ[HHb]-to-VO2p ratio for each individual was calculated as the average Δ[HHb]/VO2 relative response during the 20s to 120s period of the exercise on-transient. RESULTS: Whereas phase II τVO2p was greater (p<0.05) for MOD130 (32±11s; mean ± SD) than MOD90 (25±7s), the effective Δ[HHb] response time (τ'Δ[HHb] = τΔ[HHb] + TDΔ[HHb]) was similar between conditions (MOD90: 21±2s; MOD130: 20±1s). Despite similar steady-state reliance on O2 extraction for a given VO2p (expressed as Δ[HHb]AMP/VO2pAMP (arbitrary units; a.u.); MOD90: 14±5a.u., MOD130: 13±5a.u.), a greater transient O2 delivery-to-utilization mismatch (i.e., Δ[HHb]-to-VO2 "overshoot") was observed during the on-transient of MOD130 (1.10±0.10) compared to MOD90 (1.03±0.08) where no such mismatch was observed. CONCLUSIONS: Larger amplitude MOD transitions yielded a relatively slower adjustment of VO2p compared to smaller amplitude MOD transitions; yet, the time course of adjustment of Δ[HHb] was unaffected. The modest but significant transient Δ[HHb]/VO2 "overshoot" observed in MOD130 (but not in MOD90) suggests that within an individual, constraints imposed by a progressive attenuation of local muscle O2 delivery/distribution with increases in WR may modulate adjustments of VO2m during the on-transient of exercise. 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 | 0.001 | 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 | 0.001 | 0.000 |
| Insufficient payload (model declined to judge) | 0.003 | 0.001 |
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".