Evaluating Test–Retest Reliability and Measurement Error of the Lumbar Flexion Relaxation Ratio Within and Between Days
Bibliographic record
Abstract
The flexion relaxation ratio (FRR) of the lumbar extensor muscles is often assessed in experimental and clinical studies. This study evaluated within- and between-session test–retest reliability and measurement error for different FRR formulations. Participants completed two identical data collection sessions 1-week apart. Spine flexion and erector spinae electromyographic data were recorded during two blocks of full forward spine flexion. Participants who numerically self-reported low back pain (≥3/10) during either session were excluded from analysis. Two FRR formulations and their reciprocals were calculated. Generalizability coefficients (GC) was calculated to assess reliability. Standard error of measurement was also determined. Fifty participants were recruited, with six excluded from the analysis. Within-session reliability was moderate-to-good (GC = 0.519–0.791). Between-session reliability was poor-to-moderate (GC = 0.376–0.538). Within-session and between-session measurement errors, respectively, were 38% and 49% of the grand mean FRR. These data suggest limited FRR utility in longitudinal studies.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.005 | 0.003 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.001 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 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 teacher head, 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".