After 10 months of high-intensity circuit training, sedentary overweight women experienced a 27% increase in aerobic capacity and muscle strength, and about half of those gains remained after...
Mechanism
Synthesis from 1 study
Intense full-body workouts make muscles bigger and create more energy-producing parts inside them, which helps women get stronger and breathe better during exercise. Their bodies also keep burning extra calories after workouts and break down fat for fuel, which is why they keep most of their gains...
Most probable mechanism
When overweight women do intense full-body workouts three times a week, their muscles grow bigger from the heavy lifting, which makes them stronger and burns more calories even at rest. At the same time, their muscle cells make more energy factories (mitochondria) to use oxygen better, letting them exercise longer without getting tired. After each workout, their bodies keep burning extra calories for hours to recover, and fat stores break down to fuel this process — all of which helps them keep their gains even after stopping training for months.
Mechanical tension from resistance exercises in high-intensity circuit training activates mTOR signaling in skeletal muscle, triggering muscle fiber hypertrophy and increasing fat-free mass, which directly contributes to greater strength and elevated resting metabolic rate (10.1371/journal.pone.0202390).
Exercise-induced ATP depletion increases the AMP:ATP ratio, activating AMPK, which in turn upregulates PGC-1α to drive mitochondrial biogenesis and enhance oxidative enzyme activity, improving maximal oxygen uptake (VO2max) by 26.8% (10.1371/journal.pone.0202390).
High-intensity exercise elevates blood lactate and sympathetic nervous system activity, increasing catecholamine release that stimulates β-adrenergic receptors on adipocytes, activating hormone-sensitive lipase and promoting fat breakdown for energy use (10.1371/journal.pone.0202390).
Post-exercise oxygen consumption (EPOC) remains elevated due to restoration of ATP/PCr stores, lactate clearance, and thermoregulation, sustaining daily energy expenditure beyond training sessions and contributing to long-term metabolic adaptation (10.1371/journal.pone.0202390).
Increased fat-free mass and mitochondrial density raise basal metabolic rate and aerobic efficiency, allowing sustained energy expenditure and partial retention of VO2max and strength gains during detraining (10.1371/journal.pone.0202390).
Evidence from Studies
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