Acute intermittent hypoxia enhances volitional elbow strength, and modulates spatial distribution of muscle activation patterns in persons with chronic incomplete spinal cord injury
Bibliographic record
Abstract
Abstract Background Acute intermittent hypoxia (AIH) is an emerging technique for facilitating neural plasticity in individuals with major neurological deficits. In people with chronic incomplete spinal cord injury (iSCI), a single sequence of AIH enhances motor function such as hand grip strength and ankle plantarflexion torque, but the underlying mechanisms are not yet clear. Objective To examine how AIH-induced changes in magnitude and spatial distribution of electromyography (EMG) activity over the surface of the biceps and triceps brachii muscles contributes to improved strength. Methods Seven individuals with iSCI visited the laboratory on two occasions, at least a week apart, and received either AIH or Sham AIH intervention in a randomized order. AIH consisted of 15 brief (∼60s) periods of low oxygen (fraction of inspired O 2 = 0.09) alternating with 60s of normoxia, whereas Sham AIH consisted of repeated exposures to normoxic gas mixtures. Muscle activity of biceps and triceps brachii was recorded with high-density surface EMG during maximal elbow flexion and extension contractions. We used these EMG recordings to generate spatial maps which distinguished active muscle regions prior to and 60 minutes after AIH or Sham AIH. Results After an AIH sequence, elbow flexion and extension forces increased by 91.7 ± 33.5% and 51.7 ± 21.9% from baseline, respectively, whereas there was no difference after Sham AIH exposure. Changes in strength were associated with an altered spatial distribution of EMG activity and increased root mean squared EMG amplitude in both biceps and triceps brachii muscles. Conclusions These data suggest that altered motor unit activation profiles may underlie improved volitional strength after a single dose of AIH and warrant further investigation using single motor unit analysis techniques to further elucidate mechanisms of AIH-induced plasticity.
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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 | 0.000 |
| 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) | 0.001 | 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".