Skeletal Muscle Metabolism during an Exercise Challenge pre and post Aerobic Training in Lean and Obese Middle-Aged Individuals
Bibliographic record
Abstract
PURPOSE: To examine the effects of exercise intensity (40 and 60% VO2peak) on skeletal muscle metabolism in sedentary middle-aged lean and obese individuals, pre and post an 8 week aerobic training program. METHODS: Ten normal weight (lean) and eight obese (age, 41.0 ± 2.2 and 39.3 ± 4.7 yrs; body mass index, 24.7 ±0.7 and 36.1 ± 2.0 kg/m2; VO2peak, 40.5 ± 2.3 and 36.6 ±1.5 ml/min/kg fat free mass) volunteers cycled for 10 min at 40% VO2peak and 10 min at 60% VO2peak pre and post 8 wk of exercise training (60 min/d, 5 d/wk, 60% VO2peak). Muscle biopsies were taken from the vastus lateralis muscle at rest and following 40 and 60% of pre-training VO2peak and blood samples were obtained throughout exercise both pre and post training. RESULTS: Aerobic training improved VO2peak by ∼24 and 17% in the obese and lean groups. Muscle citrate synthase activity was similar between groups before training and increased by ∼50% in each group post training (lean, 81.5 ± 8.0 to 122.8 ± 7.9 and obese, 77.8 ± 5.7 to 118.4 ± 3.2 mmol/min/kg dm). ±-hydroxyacyl-CoA-dehydrogenase activity was also similar between groups before training and increased by ∼40% following training in each group (lean, 44.4 ± 2.2 to 61.3 ± 5.4 and obese, 47.3 ± 3.3 to 65.5 ± 4.5 mmol/min/kg dm). Exercise increased venous plasma epinephrine and whole blood lactate (La) at 60% VO2peak in both groups, with 2–3 fold higher increases in the obese group. Post training, the exercise-induced epinephrine and La increases were blunted in both groups but to a greater extent in the obese. There were no differences between groups in resting muscle La, phosphocreatine (PCr), Cr or ATP contents pre or post training. Muscle La increased during exercise at 60% VO2peak in both groups with a greater response in the obese (23.4 ± 2.9 vs. 39.9 ± 4.7 mmol/kg dm). Following training, the muscle La increase was blunted in both groups but to a larger extent in the obese. Prior to training, exercise at both power outputs decreased muscle PCr similarly in lean and obese groups (lean, 86.2 ± 3.6 to 71.4 ± 4.8 and 53.6 ±4.9 mmol/kg dm at 40 and 60%; obese, 83.9 ± 3.9 to 69.4 ± 6.0 and 48.7 ± 4.9 mmol/kg dm at 40 and 60% VO2peak). Following training there was no significant decrease in PCr at either exercise intensity in both groups. Muscle ATP content was unaffected by exercise in either group both pre and post training. CONCLUSION: Prior to aerobic training, exercise at the same relative low and moderate intensities elicited a greater whole body and skeletal muscle metabolic response in middle-aged obese vs. lean individuals. In response to aerobic training, the metabolic responses to exercise at the same pre-training power output were blunted in both groups, but to a greater extent in the obese.
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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".