Bibliographic record
Abstract
It is world knowledge that regular physical exercise increases physical fitness and reduces general health risk factors like overweight or hypertension. There is emerging evidence that regular physical exercise does also have profound effects on the brain: It affects many aspects of the brain like increasing perfusion or inducing hippocampal growth. Neurogenesis is stimulated as well as angiogenesis and increased synaptic plasticity is observed. Up to date, most data are mainly supported by animal models but human data become more and more available. There is also emerging evidence that exercise has an positive effect on pain processing: One can find anecdotal reports that runners continue to run despite stress fractures, angina and or sever blisters. But there is also experimental evidence, that athletes have increased pain thresholds and show reduced responses to noxious stimuli. Indirect measures such as raised endorphin levels in peripheral blood and cerebrospinal fluid as well as the reversibility of exercise-induced mood changes and pain perception effects by naloxone (unspecific opioid receptor antagonist) presented strong arguments for an opioidergic involvement in exercise („endorphin hypothesis”). This was also supported lately by showing opioidergic activation effects in fronto-limbic brain regions after sustained physical exercise. Based on this work and assuming central opioidergic mechanisms, we examined in an fMRI-study the effect of a two hours outdoor RUN, as compared to a control condition (two hours outdoor WALK) on pain processing in 20 right-handed male athletes (age 39.0±9.2 years, average training distance: 59.3±29.2km/week). Physical exercise was expected to affect pain processing on the behavioural and the systemic (activation) level. On the behavioural level we found a significant time x treatment interaction of the euphoria ratings, and a post-hoc significant reduction of the McGill affective subscale in the post-run condition. All other measures (including pain and sensory thresholds) were not affected. The peripheral blood endorphin levels were drastically elevated after the RUN-condition and the fMRI-analysis revealed a reduced time x treatment interaction in the antinociceptive pathway (rACC, PAG) and reduced functional connectivity of the PAG (trend). These findings suggest, that the brain seems to be in a less pain sensitive state after exercise and, therefore, the necessity to recruit the descending pain network is reduced. In conclusion, the demonstration of elevated beta-endorphin levels in plasma (RIA), the specific effect on the affective dimension of pain, and the loco-regional convergence with previous ligand PET and naloxone pharma-fMRI studies suggest an underlying opioidergic effect promoted by exercise.
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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 | 0.001 | 0.004 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.003 | 0.002 |
| Science and technology studies | 0.001 | 0.002 |
| Scholarly communication | 0.003 | 0.003 |
| Open science | 0.001 | 0.002 |
| Research integrity | 0.002 | 0.002 |
| Insufficient payload (model declined to judge) | 0.017 | 0.004 |
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".