Differences in Abdominal Muscle Activation Patterns of Younger and Older Adults Performing an Asymmetric Leg‐Loading Task
Bibliographic record
Abstract
OBJECTIVES: To determine whether differences exist between younger (20-50 years) and older adults (>65 years) in abdominal muscle amplitudes, temporal patterns, and three-dimensional (3D) pelvic motion, while performing an asymmetric leg-loading task. DESIGN: Cross-sectional. SETTING: Neuromuscular function laboratory. PARTICIPANTS: Ten healthy younger (33.3 +/- 7.7 years) and 10 healthy gender- and body mass index-matched older adults (69.0 +/- 6.6 years). INTERVENTION: Surface electromyograms from 6 abdominal muscle sites bilaterally and pelvic motions were simultaneously recorded. MAIN OUTCOME MEASURE(S): Root mean square (RMS) amplitude during the leg extension phase was calculated for each muscle. Ensemble average waveforms for the total exercise were analyzed using principal component (PC) analysis. Total angular displacement of the pelvis was calculated. Student t tests were performed on demographic and angular displacement data. Three-factor mixed model analysis of variances (group, muscle, side) tested main effects and interactions (P < .05) for the RMS amplitude and PC scores from the temporal waveforms. Bonferroni post-hoc analyses tested pair-wise differences. RESULTS: There were no between-group differences for the pelvic motions. Three PC patterns captured 85% of the variance in the waveforms. The external oblique (EO) RMS amplitudes were significantly (P < .05) higher than those of the other 3 muscle sites, similar for the PC1 scores which captured overall amplitude. The PC2 score for the internal oblique (IO) was significantly higher (P < .05) than that of all other muscles, illustrating a higher initial amplitude compared with later in the movement. There was a significant group by muscle interaction for PC3 scores, demonstrating group differences in temporal patterns. CONCLUSIONS: Both groups were able to minimize lumbopelvic motion and recruited their abdominal muscles to similar overall amplitudes, with the IO muscle activated to higher amplitudes early in the movement task. The older adult group demonstrated a distinctive drop in abdominal activity during the leg-lowering phase of the exercise and less symmetry among muscle sites.
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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 | 0.000 | 0.000 |
| 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) | 0.000 | 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".