Mitochondrial Adaptation To Training
Bibliographic record
Abstract
Skeletal muscle mitochondria are important for health and performance; however, the optimal exercise stimulus to increase mitochondrial content and function is equivocal. Counter-weighted single-leg (SL) cycling permits the comparison of training adaptations to two different protocols within the same subject, but in a manner that simulates the feeling of normal two-legged cycling. This approach provides greater statistical power to elucidate potential differences in the adaptive response to distinct training strategies. PURPOSE: To compare changes in skeletal muscle mitochondrial content and function in response to short-term high-intensity interval training (HIIT) and moderate-intensity continuous training (MICT), matched for total work. METHODS: Ten active but untrained men (age = 23±4 y, VO2peak = 46±5 mL•kg-1•min-1) performed unilateral graded-exercise tests to measure SL VO2peak and SL peak power (Wpeak). Each leg was randomly assigned to complete either six sessions of MICT (30 min at 50% Wpeak) or HIIT (4 x [5 min at 65% Wpeak and 2.5 min at 20% Wpeak]) over 2 weeks. Citrate synthase (CS) maximal activity and mitochondrial respiration in permeabilized muscle fibres were measured before and after training to assess mitochondrial content and function, respectively. RESULTS: Mean work performed per session was 144±27 kJ, with no difference between legs (p=0.91). There was a time x group interaction (p≤0.05) for both CS maximal activity and mass-specific OXPHOS capacity, such that both were higher after HIIT vs. MICT (p ≤ 0.05). CS increased from 7.4±1.4 to 10.2±2.2 and 7.6±2.2 to 8.5±2.6 mmol•kg protein-1•hour-1 (n=10) after HIIT and MICT, respectively. Mass-specific OXPHOS increased from 48±15 to 58±21 and decreased from 47±17 to 42±15 pmol•s-1•mg ww-1 (n=8) after HIIT and MICT, respectively. Mitochondrial-specific OXPHOS capacity (6.4±2.9 to 5.3±1.4 pmol•s-1• CS-1; n = 8; p = 0.30) and SL VO2peak (34±3.2 to 34±4.1 mL•kg-1•min-1; n=8; p=0.75) were unchanged in both groups. CONCLUSION: Over a 2-week training period, HIIT elicited greater increases in skeletal muscle mitochondrial content and function compared to MICT. We conclude that the intensity and/or pattern of contraction is an important determinant of exercise-induced skeletal muscle remodeling in humans. Supported by NSERC of Canada
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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 | 0.001 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.004 | 0.001 |
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".