Peak Oxygen Uptake And Muscle Oxygenation During Incremental Lifting In Healthy And Low-back Pain Subjects
Bibliographic record
Abstract
Repetitive lifting during occupational tasks has been associated with low back pain (LBP). Reductions in oxygen availability and aerobic capacity of the erector spinae muscles have been implicated in this phenomenon. This hypothesis, however, has not been tested in exercising humans. PURPOSE To compare the peak oxygen uptake (VO2peak) and muscle oxygenation responses between healthy (H) and LBP subjects during repetitive incremental lifting and lowering (RILL). METHODS Informed consent was obtained from 34 H and 34 LBP subjects who were age and gender matched. Subjects completed the prescribed RILL test: 2 min rest, 2.5 kg increase in lifting load every min to fatigue (10 lifts/min, lifting height 76 cm), 4 min of seated recovery. Cardiorespiratory responses were monitored using a wireless metabolic cart. Muscle oxygenation (Mox) and blood volume (Mbv) were recorded bilaterally from the erector spinae at the third lumbar vertebrae using near infrared spectroscopy. The following Mox and Mbv variables were calculated: delta, minimum value during RILL - resting value; range, maximum during recovery - minimum during RILL, and ½ recovery time (½ Rec, time taken for 50% recovery; an index of muscle aerobic capacity). Forward stepwise multiple regression analysis was used to predict the VO2peak from selected cardiorespiratory and NIRS variables. RESULTS There was no significant difference (p>.05) between H and LBP subjects for peak values of absolute VO2 (2.54 vs 2.29 L/min, heart rate (HR), ventilation rate, and oxygen pulse (O2 pulse). However, relative VO2peak was significantly lower (p < .05) in the LBP compared to H subjects (29.9 vs 34.4 ml/kg/ min). The LBP subjects demonstrated significantly lower Mox delta, Mox range and slower ½ Rec suggesting a reduction in muscle oxidative capacity. No significant differences were observed between groups for Mbv-delta and Mbv-range. In H subjects, peak values of HR and O2 pulse explained 59% and 16% of the common variance respectively in the relative VO2peak. In LBP subjects, peak HR, Mox-delta and peak O2 pulse explained 29%, 19% and 7% of the common variance respectively. CONCLUSIONS Localized Mox, independent of changes in Mbv, is an important predictor of the relative VO2peak in LBP but not H subjects. Support: Alberta Workers' Compensation Board and Millard Health
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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) | 0.001 | 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".