Velocity Dependent Motor Unit Discharge Rates Of The Anconeus During Elbow Extension
Bibliographic record
Abstract
Most of our understanding about motor unit properties has been derived in animals and humans from isometric contractions, in which joint angle does not change. Due to the technical difficulty of recording single motor unit action potentials during movement, especially at higher velocities, limited information exists about motor unit firing rates (MUFRs) during lengthening and shortening contractions. The unique mechanical and muscle group features of the anconeus muscle may offer a model to provide reliable recordings of MUFRs during large and fast movements of the elbow joint. PURPOSE: To determine the effect of velocity of elbow joint extension on MUFRs of the anconeus. METHODS: Motor unit recordings (n=594) from five healthy young men (∼25yrs) were collected from the anconeus during 120° range of motion of elbow extension at different velocities. Using a Biodex dynamometer, subjects first performed three brief maximal isometric contractions (MVC) at an angle of 60° of elbow flexion (0° = full extension) to determine the preload (30% MVC) for the dynamic contractions. Then, five maximal velocity elbow extensions (Max) were performed to determine the target peak velocities for the subsequent extensions. Subjects completed a number (20-40) of brief (<1s) elbow extensions at each target peak velocity (20, 40, 60, and 80% Max all at a constant load of 30% MVC) with two minutes rest between each set of extensions. Single motor unit action potentials were recorded on two independent channels, each from two pairs of indwelling wire electrodes inserted ∼3cm distal to the olecranon process of the ulna in the belly of the anconeus. RESULTS: MUFRs during MVC (∼32Hz) were 25% lower compared with MUDRs at maximal preloaded velocity of ∼500°/s (∼42Hz). From 20% to 80% Max, MUFRs increased nonlinearly from ∼13Hz to ∼23Hz. CONCLUSIONS: The anconeus may be a useful model to explore MUFRs during dynamic contractions. Preliminary results indicate that higher rates than isometric MVC are recorded during high velocity contractions, and changes in rates are related to changes in velocity. 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 | 0.002 |
| 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".