Trunk Muscle EMG Activity During Traditional Curl Ups Performed on Stable and Unstable Surfaces
Bibliographic record
Abstract
PURPOSE: To compare activation of the trunk muscles when performing traditional curl ups on one stable and three unstable surfaces. METHODS: Fifteen healthy subjects (11 female, 4 male) performed traditional curl up exercises on a bench (stable), stability ball (unstable), half dome balance trainer (unstable), and inflatable disc (unstable). Body position, tempo, and range of motion during the curl up exercise were standardized between the different surfaces. Subjects performed five repetitions, and EMG activity of the rectus abdominis, external oblique, and lumbosacral erector spinae was recorded during repetitions 3-5. The mean amplitude of the EMG signal during the different curl up conditions was normalized against the mean amplitude produced during a maximal isometric contraction. These values were analyzed using repeated measures ANOVA and paired t-tests for post hoc comparisons. RESULTS: Normalized mean EMG values for the rectus abdominis during the bench, stability ball, half dome balance trainer, and inflatable disc surfaces equaled 10.8 (+ 4)%, 10.1 (+ 3.8)%, 10.1 (+ 3.9)%, and 12.8 (+ 4.3)%, respectively. The level of rectus abdominis activation elicited by the inflatable disc was significantly higher than that resulting from the bench surface (p = .0001). No other differences in rectus abdominis activity were noted. For the external oblique the bench, stability ball, half dome balance trainer, and inflatable disc resulted in EMG values of 11.9 (+ 6.1)%, 11.9 (+ 5.9)%, 11.8 (+ 5.6)%, and 12.5 (+ 5.5)%, respectively. For the lumbosacral erector spinae the bench, stability ball, half dome balance trainer, inflatable disc yielded EMG values of 3.7 (+ 1.5)%, 3.6 (+ 1.4)%, 3.6 (+ 1.3)%, and 3.4 (+ 1.4)%, respectively. No significant differences in EMG values of the external oblique and lumbosacral erector spinae were evident between the different surfaces. CONCLUSIONS: Results indicated that curl ups performed on a stability ball or a half dome balance trainer failed to activate the abdominal musculature more effectively than when curl ups performed on a stable surface. In contrast, the inflatable disc, perhaps due to a combination of higher instability and a smaller base of support, elicited greater activation of the rectus abdominis than when compared to levels of activation during the stable curl up.
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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) | 0.001 | 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) | 0.002 | 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".