The effect of an inverted body position on lower limb muscle force and activation
Bibliographic record
Abstract
Complete inversion of the body in a seated position may occur in exceptional circumstances such as in overturned vehicles and during military maneuvers, with direct consequences on health and fatalities. However, the physiological responses to this condition have not been published previously. The purpose of this study was to compare neuromuscular responses to upright and inverted seated positions. Sixteen subjects performed maximal voluntary contraction (MVC) and submaximal voluntary contraction knee extensions (25%, 50%, and 75% of MVC) under upright and inverted seated positions. Force, quadriceps activation as measured by the interpolated twitch technique, electromyographic (EMG) activity of the vastus lateralis, and semitendenosis and evoked contractile properties of the quadriceps were measured. Results demonstrated that MVC force (p = 0.01, 6.1%) and vastus lateralis EMG (p = 0.009, 29.6%) decreased in the inverted compared with the upright position. Instantaneous strength in the inverted position was 19.3% lower than in the upright position (p = 0.005). Heart rate and diastolic and systolic blood pressures were 12.4%, 9.2%, and 10.7% lower (p < 0.0001), respectively, in the inverted position. In conclusion, a seated inverted position impaired MVC force and EMG activity, which could not be attributed to evoked contractile properties. The changes in heart rate and blood pressure may suggest inversion-induced alterations to the sympathetic nervous stimulation.
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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) | 0.000 | 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) | 0.002 | 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".