Changes in Anconeus Motor Unit Firing Rates During High-Intensity Dynamic Elbow Extensor Fatiguing Contractions
Bibliographic record
Abstract
Neuromuscular fatigue is a task-dependent process. Decreased motor unit firing rates (MUFR) have been widely reported following high-intensity isometric fatiguing protocols. However, due to technical limitations associated with tracking and discriminating single MUs, there is little known regarding the changes in MUFR following high-intensity maximal velocity dynamic fatigue. Single MU recordings can be reliably detected in the anconeus during movement, due to its distinct anatomical features, making it an attractive model for the study of neuromuscular properties during dynamic fatigue. PURPOSE: To evaluate anconeus MUFR as a function of time to task failure (TTF) during a maximal velocity elbow extension protocol using moderate to heavy loads. METHODS: Two fine-wire intramuscular electrode pairs were inserted into the anconeus to assess changes in MUFR in six male participants (25 ± 3y) over repeated sessions on separate days. Individual MUs were followed throughout a three-stage dynamic elbow extension fatigue protocol. Torque was adjusted from 45% to 35% to 25% of isometric maximal voluntary contraction (MVC) strength of the elbow extensors when 50% of the initial velocity of that stage was unattainable. This protocol was implemented to extend the task duration and to induce substantial neuromuscular fatigue. Mean MUFR was calculated for the following three relative time ranges: 0-15% TTF (beginning), 45-60% TTF (middle) and 85-100% TTF (end). RESULTS: Following the fatigue task, isometric MVC and maximal velocity at 35% MVC load decreased ~40% and ~60% compared to baseline, respectively. Mean TTF was ~80 seconds. Preliminary data from 8 anconeus MUs tracked successfully throughout the fatigue protocol indicated a reduction in MUFRs from ~36 Hz (0-15% TTF) to ~29 Hz (45-60% TTF) to ~22 Hz (85-100% TTF). CONCLUSION: During high-intensity maximal velocity dynamic contractions of approximately 1.5 minutes in duration, anconeus firing rates decreased substantially (nearly 40%). The relative decrease in MUFRs after this task is in accordance with that reported for sustained high-intensity isometric tasks in other muscles. 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) | 0.000 | 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".