Sex-based Differences Following Eccentric Exercise-induced Muscle Damage
Bibliographic record
Abstract
The response to skeletal muscle damage may be different between males and females with sex hormones proposed to be an underlying factor. Satellite cells (SC) are essential for muscle regeneration after damaging exercise with early indications suggesting a blunted response in females. PURPOSE: We aimed to comprehensively characterize the damage and SC response to eccentric exercise-induced damage in males and females. Further, we aimed to determine if possible sex differences may be attributed to levels of 17β-estradiol. METHODS: Thirty healthy males and females (21 ± 3 years [mean ± SD]) undertook 300 (30 x 10) maximal eccentric leg extension contractions on an isokinetic dynamometer, and measures were collected prior to and at six time points after exercise. Biopsies from the vastus lateralis were collected for immunohistochemical analyses. Ultrasound sonography was used to determine muscle thickness (proxy measure of swelling) and blood concentrations of 17β-estradiol and creatine kinase (CK) were determined. Measures of strength and subjective soreness were also collected. RESULTS: We observed an interaction in the CK response demonstrating a peak at 24 h (M: 536 ± 109 U/L, F: 415 ± 79 U/L); this remained elevated in males over 120 h while females returned to baseline (p < 0.05). Satellite cell content in type II fibers peaked at 72 h in males (10.1 ± 3.0 Pax7+ cells/100 fibers; p < 0.05), but the same expansion was not observed in females. An interaction was detected for muscle thickness peaking at 48 h in males (2.90 ± 0.35 cm) while females peaked instead at 72 h (2.47 ± 0.25 cm). Strength decreased significantly in both groups but was restored to baseline in males at 5 h onwards, while females only recovered at 120 h. No measures were associated with changes in circulating levels of 17β-estradiol. CONCLUSION: A sexual dimorphism in the SC response to damaging exercise was evident between males and females but was not associated with circulating 17β-estradiol.
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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) | 0.003 | 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".