Maximal Effort Repetitive Concentric Elbow Extensions Reduced Cortical And Motoneuronal Excitability In Females And Males
Bibliographic record
Abstract
Females are typically less fatigable than males when performing isometric contractions, but it is less clear if there are sex-related differences for fatigue during dynamic tasks. Further, little is known regarding fatigue-related alterations of cortical and motoneuronal excitability in response to a bout of repetitive, concentric contractions. PURPOSE: The purpose of this study was to determine how triceps brachii cortical and motoneuronal excitability is altered by a series of isokinetic, concentric elbow extensions in females and males. METHODS: Twenty-two healthy participants (12 females: 28 ± 5y; 10 males: 28 ± 5y) performed 60 maximal effort elbow extensions at an isokinetic velocity of 40°·s-1. Peak power was assessed to characterize performance fatigability. Motor evoked potentials (MEPs) from transcranial magnetic stimulation (TMS), cervicomedullary motor evoked potentials (CMEPs) from transmastoid electrical stimulation, and maximal compound muscle action potentials (Mmax) from brachial plexus electrical stimulation were evoked during a TMS-induced silent period. To isolate cortical and motoneuronal excitability, the MEP and CMEP were normalized to CMEP and Mmax area, respectively. Peripheral excitability was evaluated using Mmax area. Neural excitability was assessed during the first six (START) and last six contractions of the fatigue task. RESULTS: Peak power (START: 40.34 ± 12.08 W) decreased by 38.0 ± 12.2% (p < 0.01) with no differences between females and males (p = 0.38). Compared to START (MEP/CMEP area: 1.10 ± 0.39, CMEP/Mmax area: 0.21 ± 0.06, Mmax area: 0.14 ± 0.03 mV·s), MEP/CMEP and CMEP/Mmax decreased by 17.2 ± 87.7% (p = 0.02) and 28.8 ± 36.0% (p < 0.01), respectively, whereas Mmaxarea was unaffected by the fatigue task (p = 0.10). None of fatigue-related alterations in neural excitability were influenced by sex (p ≥ 0.27). CONCLUSIONS: Irrespective of sex, fatigue-induced reductions in peak power during repetitive, isokinetic elbow extensions is, in part, likely owing to decreases in cortical and motoneuronal excitability.
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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) | 0.005 | 0.001 |
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".