Regional Activation within the Vastus Medialis in Dynamic Contractions
Bibliographic record
Abstract
PURPOSE: Regions within the vastus medialis (VM) are known to preferentially produce knee extension force and patellar stabilization. In dynamic tasks, the central nervous system may recruit different VM regions preferentially to cope with changes in mechanical demand resulting from knee movement. The purpose of this study was to determine the effect of knee angle during the concentric and eccentric phases of dynamic movement on the regional activation within the VM. METHODS: Ten healthy women performed two tasks: A) 10 knee flexion-extension open-kinetic chain (OKC) movements between 90 and 10 degrees of knee flexion against an isotonic resistance (10% isometric maximal voluntary contraction); B) 5 closed-kinetic chain (CKC) single-leg squats. Each of the concentric and the eccentric phases of both tasks were performed in 3s. A high-density surface electromyography grid (13x5 electrodes spaced 8 mm apart) was placed across the VM. For each task, the knee angle excursion was segmented in intervals of 10 degrees, and an amplitude distribution was calculated using the average rectified value (ARV) for each channel of the grid. The location of the most active region within the VM was calculated as the barycenter of the three electrodes with the largest ARV. Two-way ANOVAs with repeated measures were used to test the effect of knee angle and phase of the movement on the location of the barycenter, separately for the two tasks. RESULTS: In the OKC task, the barycenter was more distal at more flexed knee positions (P < 0.05; total shift: 7±17 mm) and more so in the eccentric than the concentric phase (P < 0.05; 9±17 mm). Similarly, the barycenter was more distal at more flexed knee positions in the CKC task (P < 0.01; total shift: 21±18 mm) and in the eccentric phase but only between 30 and 10 degrees (P < 0.01; 13±16 mm). CONCLUSIONS: This study reveals differences in regional activation within the VM during dynamic contractions. Although large variability was observed across participants, preferential activation of the proximal VM was observed in both tasks at more extended knee positions and in the concentric phase. As regional activation may result in a different contribution of the VM as a patellar stabilizer, these findings may have implications for therapeutic exercise and for the study of mechanisms of patellofemoral pain syndrome.
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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".