MUSCULAR RESPONSE TO LIFTING WITHOUT KNOWLEDGE OF LOAD CENTER OF MASS
Bibliographic record
Abstract
It has been suggested that lifting unknown and unbalanced loads increases the risk of low back disorders. Until now, this has only been examined by altering the position of a load in the frontal plane. We investigated the response of the trunk musculature to a lifting task where the load centre of mass was altered in both the frontal and sagittal planes, without disclosing its location. Ten male participants lifted a covered bin with handles that was divided into 9 compartments in which a 7 kg load was placed (total load lifted, 13 kg). EMG was recorded bilaterally for the upper and lower erector spinae (UES, LES), latissimus dorsi, and the external oblique muscles. Peak EMG of the UES and LES (right and left) was significantly affected by the load position (all p < 0.001). UES activity was highest on the same side as the load, while the highest LES activity was found on the contralateral side, this was accentuated with loads nearest the lifter. Load position significantly affected the latissimus dorsi (right and left) and the left external oblique activity (p < 0.05) but not the right external oblique. With peak activations of 5–7% MVC, the latissimus dorsi and oblique muscles were not analyzed further. The effect of load position in the sagittal plane was examined by collapsing the data across the compartments in the frontal plane giving three load distances (26, 40 and 54 cm) from the lifter. With the load in the nearest row, the UES activity was 25% (left) and 23% (right) higher than in the farthest row (both p < 0.0002), with a peak activity level of 36% MVC. Similarly, LES activity was 14% (left) and 12% (right) higher in the nearest versus the farthest row (both p < 0.01), reaching a peak of 45% MVC. Given that the load lifted was not considered 'heavy' by most standards, the high muscle activity levels are of concern due to the implications for asymmetrical loading of the intervertebral discus. Although preliminary, this study indicates that further research is required to determine the full importance of the knowledge of load characteristics on lifting safety.
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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 | 0.002 |
| 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) | 0.003 | 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".