Quantification of the Lumbar Flexion-Relaxation Phenomenon: Comparing Outcomes of Lumbar Erector Spinae and Superficial Lumbar Multifidus in Standing Full Trunk Flexion and Slumped Sitting Postures
Bibliographic record
Abstract
OBJECTIVE: The purpose of this study was to identify differences in flexion-relaxation outcomes in asymptomatic participants, with respect to both flexion-relaxation phenomenon (FRP) occurrence and spinal onset angles, as a function of posture and choice of muscle being examined. METHODS: This was a cross-sectional study in a laboratory setting. Thirty asymptomatic participants performed standing full trunk flexion and slumped sitting postures while activation levels of the lumbar erector spinae and superficial lumbar multifidus were monitored. Two thresholds were used to define whether FRP was present in each muscle and, if present, at what trunk flexion angle it occurred. These outcomes were compared descriptively between muscles and between postures. RESULTS: Most participants displayed FRP in both muscles during standing full flexion; occurrences were more variable in slumped sitting. On average, FRP during standing full flexion and slumped sitting occurred at approximately 80% and 52% of participants' maximum flexion value, respectively. Variability in the slumped sitting onset angles was greater than that in standing full flexion. CONCLUSION: Outcomes for FRP during standing full flexion in asymptomatic participants appeared to be more robust and were not affected by the choice of either lumbar erector spinae or superficial lumbar multifidus. Conversely, during slumped sitting, FRP occurrence varied substantially depending on choice of muscle, although onset angles were relatively consistent between muscles. Although the choice of one muscle over the other may be warranted, it may be prudent to examine both muscles during FRP investigations in sitting postures, in order to fully characterize the behavior and activation patterns of the lumbar musculature.
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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 | 0.003 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 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".