Effect Of Elbow Joint Angle On Anconeus Fascicle Length And Motor Unit Firing Rates
Bibliographic record
Abstract
In a pilot study of motor unit firing rates (MUFRs) during concentric contractions in the anconeus we showed curvilinear increases in MUFRs with increasing velocity of elbow extension at a constant load. Motor unit firing rates were also greater at a given intensity for dynamic compared with isometric elbow extension. Although the elbow angle was changed substantially during the dynamic contractions, the actual length change of the anconeus is not known. PURPOSE: To determine the effect of elbow angle on fascicle length (FL) and pennation angle (PA) of the anconeus muscle and to relate these results to MUFRs during dynamic contractions. METHODS: Motor unit recordings (n=∼200) from six healthy young men were collected from the anconeus over 120° of elbow extension at a target velocity of 25% of maximal velocity and at a constant load of 25% maximal isometric elbow extension (MVC) torque using a Biodex dynamometer. Single motor unit action potentials were recorded from two pairs of indwelling wire electrodes inserted ∼3cm distal to the olecranon process of the ulna in the belly of the anconeus. In a separate experiment, the FL and PA of the anconeus muscle were assessed from eight subjects using a b-mode diagnostic ultrasound unit at 0°, 45°, 90° and 135° of elbow flexion with 0° representing full extension. RESULTS: Average MUFR was 11.5±2.4Hz for 25% MVC. For dynamic elbow extension, MUFRs were 13.8±2.4Hz, 16.7±3.5Hz, 24.1±4.8Hz and 36.6±12.1Hz at 25, 50, 75 and 100% of maximum velocity, respectively. Fascicle length increased 128% from full extension to 120° elbow flexion, whereas PA of 120° (12°) decreased to 75% of PA at full extension (16°). CONCLUSIONS: These data suggest there is a change in overall muscle length as indicated by changes in both FL and PA over the range of elbow joint angles. Thus, it seems that MUFRs can be reliably recorded across various velocities in the anconeus during muscle length changes which may explain the differences observed between isometric and dynamic MUFRs. 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) | 0.002 | 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".