Seven Interval Training Sessions Increases Skeletal Muscle Capacity for Fat Oxidation in Active Females
Bibliographic record
Abstract
Endurance training has been demonstrated to increase the capacity for fat oxidation, and recently 2 weeks of short-term sprint interval training has been demonstrated to increase skeletal muscle activity of citrate synthase (CS). However, the effects of lower-intensity interval training (∼90% VO2max) protocols on muscle metabolism have not been investigated. PURPOSE: We aimed to investigate whether seven high-intensity interval training sessions could increase skeletal muscle capacity for fat oxidation and alter substrate utilisation during 1 hr of cycling in active females. METHODS: Eight active females participated in the study. Following assessment of VO2max and familiarisation trials, subjects cycled for 1 hr at 62% of VO2max (PRE) with expired gas and blood collected during exercise, and skeletal muscle biopsies obtained from vastus lateralis immediately prior to and following exercise. Subjects then rested for a minimum of 2 days prior to entering the interval training period which involved 7 × 1 hr sessions of cycle ergometer interval training (10 repeats of 4 min intervals at 90% of VO2max with 2 min recoveries) conducted every other day over a 2 week period. Subjects then performed a final 1hr ride 2 days after the final training session (POST). RESULTS: VO2max increased by 12% as a result of training and the 1hr exercise intensity POST was 53% of the new VO2max. Whole body RER decreased and estimated fat oxidation increased POST compared with PRE (p<0.05; mean RER of 0.90±0.01 vs. 0.86±0.02 over 1hr of exercise). Activities of CS and β-HAD were both significantly increased (p<0.05) in baseline muscle biopsies obtained POST vs. PRE (CS, 29.3±1.6 vs. 24.5±1.9 and β-HAD, 20.4±1.4vs. 15.4±1.6 umol/g wet muscle/min). No significant difference was observed in muscle glycogen content (mmol glucosyl units/g dry muscle) at baseline between PRE and POST trials (469±25 vs. 475±26), but glycogen content after 1hr exercise was significantly lower (p<0.05) PRE compared to POST (137±17vs. 182±15). Plasma epinephrine (nM) was lower during exercise POST compared with PRE (at 1hr: 0.75±0.12vs. 1.10±0.15, p<0.01) and blood lactate was also lower POST. There was no difference in baseline or 1hr exercise concentrations of muscle PCr, Cr, ATP, or lactate. Skeletal muscle total content (arbitrary units) of FABPpm was increased from PRE to POST training (1034±124 vs. 1289±124 AU, p<0.01) but no change was observed in FAT/CD36 protein content (867±96 vs. 888±79 AU). CONCLUSION: High-intensity interval training over only 2 weeks in active females induces a marked increase in whole body and skeletal muscle capacity for fat oxidation during exercise, resulting in glycogen sparing.
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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".