Cerebral and Muscular Oxygenation/Blood Volume Responses to Resistance Exercise under Normoxia and Hypoxia in Healthy Subjects
Bibliographic record
Abstract
During hypoxia (H), there is a systemic reduction in %SaO2 that can affect both cerebral and muscular oxygenation and blood volume (COX, MOX, CBV, MB V) at rest. We have demonstrated that H impairs resistance exercise (RE) performance. However, whether this decline is due to reduced neuronal activation or localized muscle impairment is not known. PURPOSE: To examine the effects of acute H on the COX, CBV, MOX and MBV responses to unilateral knee extensions (KEX) at 50, 75 and 100% of 1RM. METHODS: 24 healthy subjects (10 F, 14 M) consented to participate in 3 test sessions, at least 48 h apart. They randomly performed 1 set of KEX at 50, 75 or 100% 1 RM until volitional failure under normoxia (N; FiO2=0.21) and hypoxia (H; FiO2=0.14). The protocol consisted of 2-min baseline, 5-min rest (H or N), KEX, 4-min recovery, 5-min rest (N or H), KEX, and 4-min recovery. At 50 and 75% 1RM, KEX was performed dynamically with a controlled cadence (CON and ECC phase at 2 s each), and at 100%, isometrically (knee fully extended). Changes in COX, CBV, MOX, and MBV were monitored by continuous wave near infrared spectroscopy (MicroRunman, NIM Inc, PA). The probes were placed over the motor point of the vastus lateralis of the dominant leg and on the contralateral frontal lobe. Delta values (RE-rest) were used for analysis in a 3-way repeated measures ANOVA model. RESULTS: Endurance time was significantly reduced during H (50%: 55.4±9.3; 75%: 34.9±6.9; 100%: 38.5±14.3) compared to N (50%: 59.7±12.8; 75%: 37.9±8.0; 100%: 42.4±14.8). COX and CBV increased and MOX and MBV decreased during RE under both conditions. No significant differences between N and H for COX (N: 0.037±0.003, H: 0.042±0.005; P=0.215), CBV (N: 0.073±0.006, H: 0.078±0.007; P=0.274), MOX (N: −0.158±0.11, H: −0.153±0.012; P=0.479), and MBV (N: −0.205±0.017, H: −0.204±0.015; P=0.930) were observed at any of the intensities. CONCLUSION: These findings suggest that the lower endurance under H is not due to reductions in neuronal activation or oxygen availability in the muscle. At the point of fatigue, alterations in the cerebral and muscle oxygenation are independent of the intensity of muscle contractions.
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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) | 0.001 | 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".