AN ALTERNATIVE TECHNIQUE TO EXAMINE THE FORCE-FREQUENCY RELATIONSHIP IN HUMAN SKELETAL MUSCLE
Bibliographic record
Abstract
We devised a method to assess the force-frequency relationship in human skeletal muscle that can be administered in 3s, is well tolerated by subjects (n = 10) and is sensitive to low frequency fatigue. The method consists of a single 3s train of shocks delivered directly to the femoral nerve. The frequency of the train increases rapidly and exponentially over 3s from 5 to 100 Hz. The force response of the knee extensors to this increasing frequency train (IFT) was compared to that of a standard series of constant frequency trains (CFT), where is trains of shocks are delivered at single frequencies, ranging from 5 to 100Hz. Both force-frequency curves were examined in two conditions known to alter contractile properties. First, we changed the knee angle to alter muscle length and, in separate experiments, induced muscular fatigue by having subjects perform repeated isometric contractions until the target force was unattainable. Because the frequency required to produce 50% of peak force (50%) was not different between stimulation protocols, we conclude that there was no leftward shift in the curve when the knee extensors were shortened. In contrast, we observed a rightward shift in the curve after fatigue with both protocols; the f50% increased by 48% (p < 0.01) with CFT and 58% (p < 0.001) with an IFT. Low frequency fatigue, as assessed by the ratio of forces produced at 20 and 50Hz stimulation (20:50 ratio), was marked during recovery. The CFT produced an irregular pattern of low frequency fatigue recovery, but the IFT 20:50 ratio, which was most depressed immediately following fatigue, increased smoothly and by 300s was not different from control. These experiments show that the IFT stimulation protocol reveals the same alterations in muscle performance as the traditional CFT. Moreover, the IFT requires only 3s to administer and was judged more tolerable by 70% of our subjects. This suggests that the technique may be an effective alternative for determining the force-frequency relationship in human muscle for clinical and experimental purposes. 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 | 0.001 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.004 | 0.001 |
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".