Frequency Dependent Rate Of Torque And Velocity Development In Human Knee Extensors
Bibliographic record
Abstract
PURPOSE: Early and late rates of torque and velocity development (RTD and RVD, respectively) during muscle contractions are important for sport and daily tasks. Electrically evoked contractions can be used to explore the relationship between activation rate (i.e., frequency) and RTD or RVD. However, the relationships between stimulation frequency and early or late RTD and RVD of electrically evoked contractions have not been explored, which may provide insight into the activation determinants of rapid contractions. METHODS: The right knee extensors of healthy adults (age = 26 ± 4 years, n = 10) were tested on a HUMAC-NORM dynamometer. Stimulating electrodes were secured across the proximal and distal anterior thigh. The current for evoked contractions was set to produce ~50% of isometric maximal voluntary contraction (MVC) torque during 100 Hz stimulation. Isometric (90° joint angle) and isotonic (loaded to 7.5% MVC torque from 90° to 150° range of motion) contractions were electrically evoked at 1, 5, 7.5, 10, 12.5, 15, 17.5, 20, 25, 30, 40, 50, 75, and 100 Hz (20 seconds of rest between frequencies) each for 2 seconds or until range of motion was achieved. Early (0 to 50 ms) and late (0 to 100 ms) isometric RTD and isotonic RVD were evaluated at each frequency, normalized to 100 Hz. Relationships between frequency and RTD or RVD were fitted to a sigmoid function, and the slope of the steep portion and plateau frequency (segmental regression) were compared. RESULTS: All relationships were well fitted by a sigmoid function (r2 = 0.95 to 0.99). Early RTD displayed a significantly lower slope (~55% lower, p < 0.01) during the steep portion of the curve and a higher plateau frequency (~50 vs. ~32 Hz, p < 0.01) compared with late RTD. However, no differences between early and late RVD were observed for the slope (~5% lower, p = 0.29) and plateau frequency (~31 vs. ~31 Hz, p = 0.62). CONCLUSION: Early and late phase RTD and RVD display a sigmoid relationship with frequency, but early RTD is more dependent on stimulation frequency, whereas RVD and late RTD plateau at a lower frequency. These results indicate that early RTD during a rapid voluntary contraction may be more dependent upon a high rate of neural activation, whereas RVD and late RTD may be more dependent upon other factors. 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".