Torque-Length Relationship And Voluntary Activation Of The Human Triceps Brachii
Bibliographic record
Abstract
The effect of joint angle on maximum voluntary isometric torque (MVC), electrically evoked contraction torque, and voluntary activation have not been evaluated comprehensively and systematically in the human triceps brachii. PURPOSE: To compare the effect of joint angle on isometric MVC, evoked doublet amplitude, and voluntary activation (VA) assessed by a modified twitch interpolation technique. METHODS: Using a Biodex System 3 dynamometer, seven men performed 5 s MVCs at several joint angles including short (40°), neutral (80°), and long muscle lengths (120° of elbow extension). At each angle, doublets were evoked during the MVC to examine the interpolated doublet amplitude. Immediately following the MVC at each angle, doublets were elicited at rest, and superimposed on a 2 Nm (~ 4% of MVC), and a 5 Nm (~ 9% of MVC) brief (~ 3 s) sustained contraction. The order of the post-MVC doublets was randomized among subjects. Percentage VA [assessed as (1-(interpolated doublet/post-MVC doublet))x100] was compared across muscle lengths using the three different post-MVC doublet amplitudes evoked at rest (0 Nm), 2 Nm, and 5 Nm. RESULTS: MVC torques were similar at all muscle lengths (50-60 Nm). The interpolated doublet (~ 2 Nm) also did not change with muscle length but in contrast, all post-MVC doublets were significantly larger at 120° (~25 Nm) compared to either 40° or 80° (10 -15 Nm). At 40°, the 0 Nm and 5 Nm post-MVC doublet amplitudes were similar but were significantly lower than the post-MVC 2 Nm doublet torque, but the post-MVC doublet amplitudes evoked at 80° and 120° were not different. At rest, VA was greater at 120° (~95%) compared to either 40° or 80° (~ 80% and ~ 86%, respectively). Using the post-MVC 2 Nm doublet significantly increased VA by ~7% at 40° compared to VA assessed using the post-MVC doublet at rest. CONCLUSION: Elbow extensor MVC torque in the triceps brachii was not affected by changes in muscle length. The interpolated doublets also were similar at all lengths but post-MVC doublet amplitude decreased at shorter (40° and 80°) muscle lengths. Finally, a low torque contraction of 2 Nm post-MVC improved the assessment of VA at the shortest muscle length (40°). Supported by NSERC and OGS.
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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".