Effect Of Tendon Vibration On Elbow Flexor Force Steadiness And Motor Unit Activity In Men And Women
Bibliographic record
Abstract
Motor unit (MU) discharge rates are higher in the short head compared with the long head of the biceps brachii in the supinated forearm position, but do not differ between neutral and pronated positions (Harwood et al. 2008). Elbow flexor force steadiness in men is better in the supinated position compared with neutral and pronated. Differences in force steadiness and MU activity may occur through alterations in afferent feedback. Tendon vibration alters 1a feedback through excitation of the muscle spindle. Little is understood about steadiness in women, but because women are weaker steadiness is likely to be less relative to men. PURPOSE: To quantify the effects of tendon vibration in young men and women on force steadiness and motor unit properties of the biceps brachii during isometric elbow flexion in a supinated position. METHODS: Eight males and eight females (20-24 years) performed tracking tasks with the non-dominant arm. Force was slowly increased (7.5s) to 15% maximum voluntary contraction (MVC), held for 35s, and then decreased (7.5s) to resting baseline levels. Vibration (100Hz) was applied to the biceps tendon for 5s in the middle of the 35s isometric holding phase. Individual motor units were recorded from the short and long head of the biceps brachii with fine wire electrodes. RESULTS: Force steadiness was greater in men (Pre, 1.3 + 0.2%; Post, 2.0 + 0.9%) compared with women (Pre, 1.8 + 0.6%; Post, 2.46 + 1.0%) and decreased in both groups with the application of vibration (P<0.001). There was no difference in MU activity between the short and long heads of the biceps brachii (p=0.08). Motor unit discharge rates (p=0.003) and discharge rate variability (p=0.01) were lower in men compared with women. In men and women, MU discharge rates prior to vibration (15 + 2 Hz) were higher compared with post vibration (13 + 3 Hz) and recruitment thresholds were also lower after vibration. Forty-nine MUs were recorded prior to vibration, whereas 64 MUs were recorded following vibration. CONCLUSIONS: The decrease in force steadiness in the biceps brachii after the application of vibration may be associated with more motor units being active and discharge rates being less. Alterations in afferent feedback through spindle excitation unlikely account for differences in steadiness and MU activity between heads.
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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) | 0.003 | 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".