The Effect of Muscle Length on Transcranial Magnetic Stimulation-induced Muscle Relaxation Rate
Bibliographic record
Abstract
Muscle relaxation rate is an important intrinsic contractile property that influences the neural drive necessary to achieve a desired force. Most relaxation data are obtained at rest through evoked contractions; however, the application of transcranial magnetic stimulation (TMS) during a maximal voluntary contraction (MVC) allows for an in vivo (i.e., a more functionally-relevant) measurement of muscle relaxation. PURPOSE: The purpose of this study was to determine if TMS-induced relaxation is sufficiently sensitive to detect changes in plantar flexor muscle length when all synergists are actively engaged and the ankle joint angle is varied. METHODS: Seven males (24.3 ± 7.3 years; mean ± SD) performed a total of 21 brief (~3s) isometric plantar flexor MVCs in a prone position at full knee extension, randomized between 20° dorsiflexion (DF), a neutral ankle position (0°), and 30° plantar flexion (PF). During each MVC, high-intensity TMS (80% of stimulator output) was delivered to the motor cortex with a double-cone coil attached to two magnets via a BiStim unit. Peak relaxation rate was calculated to be the steepest slope of the TMS-induced drop in torque. RESULTS: MVC torque was significantly greater in the dorsiflexed (178.6 ± 35.5 Nm) compared to neutral position (144.2 ± 19.6 Nm) and in the neutral compared to plantar flexed position (59.0 ± 10.0 Nm). Peak relaxation rate was equivalent at 20° DF (-2060.3 ± 626.7 Nm/s) and 0° (-1944.8 ± 259.9 Nm/s) and both rates were significantly faster compared to the rate at 30° PF (-794.1 ± 203.9 Nm/s). CONCLUSION: Absolute relaxation rate was markedly slower when the plantar flexor muscles were placed in a shortened position, which indicates that TMS is sufficiently sensitive to detect changes in muscle length. These results support published data which demonstrate an ability of TMS to detect changes in muscle relaxation rate due to temperature, fatigue, stimulus intensity, and synergist contribution. Supported by NSERC, CFI and BCKDF
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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) | 0.002 | 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".