Peripheral Transmission Failure Confounds Estimates of Central Fatigue made using Single and Paired-Pulse TMS
Bibliographic record
Abstract
0081 Caffeine is a central nervous system stimulant that has ergogenic effects on the voluntary activation of human muscle. The drug is therefore useful in studying central fatigue. PURPOSE: We set out to assess the intracortical contribution to fatigue using paired-pulse transcranial magnetic stimulation (p-pTMS), and determine whether the effects of caffeine are mediated intracortically. METHODS: Nine men attended 3 sessions (caffeine – 6 mg/kg, placebo, and control) in this double-blind, repeatedmeasures study. Each session consisted of: 1) pre-capsule test 2) drug administration and 1-hr rest, 3) post-capsule test, 4) fatigue task, 5) recovery measures. Pre-capsule, post-capsule and recovery tests consisted of maximal voluntary contractions (MVC), maximal twitch and M wave of the first dorsal interosseous (FDI), and a paired-pulse paradigm. The fatigue task was an intermittent, submaximal, isometric finger abduction protocol. The paired-pulse paradigm included 10 single-pulses and 40 pulse-pairs with interpulse intervals of 1 ms, 3ms, 10 ms, or 12 ms applied in random order. The TMS output of the conditioning pulse was 80% of resting motor threshold (RMT), and 120% RMT for the test pulse. RESULTS: The motor evoked potential (MEP) was diminished at short interpulse intervals (1 and 3 ms), and increased at long intervals (10 and 12 ms). Neither caffeine nor fatigue had an effect on either intracortical inhibition (ICI) or facilitation (ICF) measured using the p-p paradigm. However, the MEP evoked by the single pulse declined more than 40% (p<0.01) in all three drug conditions. Because the M wave also declined by more than 40% (p<0.01), the test pulse MEP was normalized to the M wave. When normalized, single-pulse MEP did not decline following the fatigue protocol. CONCLUSIONS: Although there was a fatigue-induced decline in the single-pulse MEP, this was due to peripheral rather than central failure. Neither fatigue nor caffeine effected p-pTMS estimates of ICI and ICF. Furthermore, p-pTMS studies that increase stimulator output to maintain a constant test MEP amplitude post-fatigue may be confounded by peripheral transmission failure. Supported by NSERC Grant A6655 and a Research Grant on Human Performance and Injury Prevention from the ACSM Foundation.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| 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 | 0.001 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 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 teacher head, 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".