The History Dependence of the EMG‐Force Relationship during Ankle Dorsiflexion
Bibliographic record
Abstract
The steady‐state isometric contraction following a shortening or lengthening muscle action shows distinctly different force and activation levels as compared with a purely isometric contraction at the same muscle length. This study investigated how prior active lengthening (residual force enhancement; RFE) and shortening (force depression; FD) influences the isometric electromyography (EMG)‐Force relationship at submaximal and maximal levels as compared with purely isometric (ISO) contractions. By utilizing a series of force clamps and activation clamps at 20%, 40%, 60%, 80% and 100% of maximal isometric voluntary contraction (MVC) and maximal isometric integrated EMG (iEMG), respectively, the relative differences in neuromuscular efficiency (e.g., force/iEMG) between ISO, RFE, and FD were investigated. 17 healthy young male subjects were seated on a cybex dynamometer and performed voluntary contractions of the ankle dorsiflexors. Subjects first performed an MVC to determine relative intensities, then performed randomized active lengthening and shortening contractions at 25 deg/s over a 25 deg excursion ending at 115 degs respectively. These contractions were then compared with the purely isometric contraction at 115 degs. Surface EMG was used to record from tibialis anterior and soleus. In the RFE state when compared to the ISO state, there was significantly higher torque production during 100% MVC (~7%, P<0.05) with no significant change in agonist iEMG. Submaximally, less agonist iEMG was required to achieve the same amount of force at 60% MVC (P<0.05), and approaching significance for 40% and 20% MVC (P=0.07 and P=0.06 respectively), indicative of increased neuromuscular efficiency. In the FD state compared to the ISO state it was found that there was significantly less force produced during MVC (~15%, P<0.0001) with no significant change in agonist iEMG, but an increase in antagonist iEMG (P<0.05). In the submaximal FD state there was more agonist iEMG required to achieve the same levels of force at 80%, 60%, 40%, and 20% MVC (P<0.05), accompanied by significant increases in antagonist iEMG at 60% and 40% MVC (P<0.05). From these results, it can be concluded that the history dependent states have independent EMG‐Force relationships that exhibit significantly different levels of neuromuscular efficiency than the isometric EMG‐Force relationship. Support or Funding Information NSERC ‐ Natural Science and Engineering Research Council of Canada
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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".