Changes In VO2 And Muscle Deoxygenation Kinetics With Training In Old And Young Adults
Bibliographic record
Abstract
Phase II pulmonary VO2 (VO2p) kinetics are slower in older (O) than in younger (Y) adults. Training results in a faster VO2p kinetics in both O and Y, however, the time-course and mechanisms underlying this faster adaptation are unknown. PURPOSE: To determine the time-course and mechanisms of adaptation for phase II VO2p time constant (tVO2p) in O and Y men in response to a 12-week endurance training program. METHODS: VO2p and muscle deoxygenation kinetics were examined during step transitions from 20 W to moderate-intensity cycling (90% of estimated lactate threshold) in 8 O (68 (7) yr; mean (±SD)) and 8 Y (23 (5) yr) men pre-training, and at 3, 6, 9, and 12 weeks of training. VO2p was measured breath-by-breath using a volume turbine and a mass spectrometer. Changes in deoxygenated-hemoglobin concentration ([HHb]) of the vastus lateralis muscle were measured by near-infrared spectroscopy. VO2p and [HHb] were modeled with a mono-exponential using non-linear regression. Training was performed on a cycle-ergometer three times per week for 45 min at ∼70% of VO2peak; training intensity was adjusted at 3 week intervals to reflect changes in fitness level. RESULTS: Pre-training tVO2p was greater (p<0.05) in O (43 (11) s) than Y (34 (8) s). The tVO2p decreased (p<0.05) by 3 weeks training in both O (35 (9) s) and Y (22 (8) s) with no further changes seen with continued training: tVO2p at 12 weeks was 32 (7) s (O) and 20 (7) s (Y). Pre-training, [HHb] adaptation (MRT=TD+t) was faster than tVO2p in both O and Y, which resulted in the [HHb]/VO2 displaying a transient "overshoot" relative to the subsequent steady state level. After 3 weeks training the [HHb]/VO2 "overshoot" was attenuated in both O and Y. With further training, the "overshoot" persisted in O but was eliminated in Y. CONCLUSION: The training-induced speeding of VO2p kinetics in O and Y at 3 weeks of training (i.e., reduced tVO2p) appeared to be the result of an improved (microvascular) blood flow distribution (as represented by a lower [HHb]/VO2). The continued "overshoot" in the [HHb]/VO2 in O, but not Y, may reflect a reduced vasodilatory responsiveness that may limit muscle blood flow distribution (and O2 delivery) at exercise onset and thus limit further speeding of VO2 in O. Supported by: CIHR, NSERC, Standard Life Assurance Company of Canada.
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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".