In men who already lift weights, doing resistance training with the same total workload and pushing to muscle failure can increase muscle mass and decrease fat mass, even if their diet does not...
Mechanism
Synthesis from 1 study
Lifting weights until you can't do another rep forces your muscles to work harder than usual, making them grow bigger over time. At the same time, the intense effort burns so much energy that your body starts using stored fat for fuel, helping you lose fat—even if you don't change what you eat.
Most probable mechanism
When you lift weights until you can't do another rep, your muscles get tired and your body has to call on more powerful muscle fibers to keep going. This forces more muscle fibers to work hard, which triggers them to grow bigger over time. At the same time, the intense effort burns a lot of energy and forces your body to use stored fat for fuel, helping you lose fat even if you don't change what you eat.
Metabolic byproducts accumulate in fatigued slow-twitch muscle fibers during repeated contractions to volitional failure, reducing their force-generating capacity.
The central nervous system responds by recruiting high-threshold motor units that control fast-twitch muscle fibers to maintain required force output.
Recruitment of high-threshold motor units increases mechanical tension and metabolic stress across a greater proportion of muscle fibers.
Elevated mechanical tension and metabolic stress activate intracellular signaling pathways, including mTOR, that stimulate muscle protein synthesis and satellite cell activity.
Increased muscle protein synthesis leads to net accretion of contractile proteins and muscle fiber hypertrophy, raising fat-free mass.
The high energy demand of prolonged, fatiguing contractions elevates systemic metabolic rate and increases reliance on adipose tissue as a fuel source.
Chronic energy expenditure from repeated training sessions without compensatory caloric intake creates a sustained negative energy balance in adipose tissue, promoting lipolysis and fat mass reduction.
Evidence from Studies
Supporting (1)
Community contributions welcome
The Effect of Different Resistance Training Load Schemes on Strength and Body Composition in Trained Men
Contradicting (0)
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