Pre-frontal Cortex Oxygenation Is Altered During 20km Time Trial (20tt) In Acute Hypoxia Vs. Normoxia
Bibliographic record
Abstract
Recent research has shown that reduced muscle force and power during maximal voluntary contractions is related to both central and peripheral fatigue. Furthermore, some studies have investigated this central-peripheral relationship by comparing normoxia vs hypoxia during incremental exercise and found that a greater deoxygenation in the pre-frontal cortex likely contributed to exercise termination during hypoxia. We hypothesized that the response in pre-frontal cortex deoxygenation during endurance exercise would be greater during hypoxia and would contribute to a reduced power output. PURPOSE: To determine the effects of pacing strategy during intense cycling performance on pre-frontal cortex oxygenation under hypoxia and normoxia. METHODS: Eight competitive male cyclists (VO2max=57±5.8mL•kg−1•min−1) completed two 20TT in random order in a normobaric chamber on their own bicycles mounted on a Computrainer. In one trial, the 1st 10 km was normoxic (FIO2=21%) and the 2nd 10 km was hypoxic (FIO2=15% ∼2700 m). The order was reversed in trial two (21-15; 15-21). Subjects were blinded to the conditions. Near infrared spectroscopy was used to monitor pre-frontal cortex oxygenated (HbO2), deoxygenated (HHb) and total (tHb) hemoglobin concentration changes. RESULTS: ANOVA showed statistical (p≤0.05) differences between trials for all variables. There was a greater HHb during hypoxia, regardless of whether it was performed during the first (21-15) trial (0.29±0.24μM) or the second (15-21) trial (0.36±0.26μM). The HbO2 data showed a similar response in that a significantly greater HbO2 occurred under hypoxic conditions regardless of trial order. During the 21% trial HbO2 change was 0.31±0.48μM and 0.51±0.21μM change during the 15% trial. tHb demonstrated a similar pattern showing an increase during the hypoxic (0.87±0.33μM) vs normoxic condition (0.57±0.41μM). During each trial, there was a "cross-over" in the HHb, HbO2, and tHb response corresponding to the imposed condition (21% or 15%). Changes in power output (PO; Watts) were significantly correlated with HHb (r=-0.53), HbO2 (r=0.73), and tHb (r=0.57) during the 21-15 protocol, and moderately correlated with HHb (r=-0.47), and tHb (r=0.57) during the 15-21 protocol. PO was also lower during hypoxia vs normoxia and showed the same "cross-over" response as the pre-frontal cortex data. CONCLUSION: These data suggest that changes in pre-frontal cortex HHb and HbO2 correspond to changes in PO suggesting that central and peripheral factors contribute to the pacing strategy needed to complete this type of intense exercise. Support: NSERC Canada, Kingston University, University of Cape Town
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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) | 0.002 | 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".