CORTICAL EXCITABILITY DURING NEUROMUSCULAR FATIGUE AND RECOVERY IN CAFFEINE RESPONDERS
Bibliographic record
Abstract
We have repeatedly demonstrated a typical distribution of caffeiine (CF) responders (subjects who increase endurance time of isometric contractions by greater than 5% in a CF vs placebo trial) and nonresponders. In this randomized, double-blind, repeated measures study, 8 male subjects reported to the laboratory on 2 days. Following baseline data collection, subjects received a CF (6 mg/kg) or placebo (PL) capsule. After a 1 hr rest, transcranial magnetic stimulation (TMS), surface EMG, M wave and twitch data were collected from the first dorsal interosseous (FDI) before, during and for 15 min following a bout of intermittent isometric contractions. We hypothesized that CF would increase cortical excitability (CE) during the fatigue protocol and that this would account for the increased endurance time (Tlim) in responders. Of the 8 subjects, 5 were responders. Tlim of the responders was 33% greater in the CF compared to the PL trial. Maximal voluntary contraction (MVC) was decreased by 26% following the fatiguing contractions. The decline in MVC was accompanied by 28% reduction in the EMG. Peripheral transmission failure did not account for this reduction. CF did not alter pre-fatigue CE, but potentiated CE markedly following the first set of contractions. CE declined rapidly over the remained of the fatigue protocol and was depressed to the same extent at Tlim in both the CF and PL trials. MVC partially recovered, whereas maximal EMG and twitch amplitude did not recover at all during the 15 min recovery period. CE recovered completely in the CF trial but remained depressed in the PL trial. Increased CE had no effect on the recovery of force or maximal EMG which occurred at the same rate in the CF and PL trials. Twitch amplitude remained depressed throughout the 15 min recovery period in both the CF and PL trial and was likely the cause of the delayed recovery of force producing capacity in both trials. These data suggest that cortical excitability may play a role in the ergogenic effect of caffeine during repeated submaximal isometric contractions. 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) | 0.001 | 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".