People who have not previously trained may experience different muscle growth patterns from those who have been training regularly, when exposed to the same exercise routines.
Mechanism
Synthesis from 4 studies
When you first start lifting weights, your muscles grow fast because your body is super responsive to the stress — it turns on growth signals strongly and recruits more cells to help build muscle. After you’ve trained for a while, your muscles get better at handling that same stress, so they don’t...
Most probable mechanism
When someone starts lifting weights, their muscles respond strongly because they haven't been exposed to this kind of stress before — the cells sense the tension and chemical changes from exercise and turn on growth signals more easily. As someone trains more, their muscles adapt by becoming more efficient at using those signals, so the same workout doesn't trigger as big a response. This means beginners grow faster because their bodies are more sensitive to the signals that build muscle, while trained people need more intense or varied training to keep growing.
Resistance exercise generates mechanical tension and metabolic stress within muscle fibers, activating mechanosensors and intracellular signaling pathways including mTORC1
mTORC1 activation increases ribosomal biogenesis and protein translation, driving myofibrillar protein synthesis and muscle fiber growth
Metabolic stress and muscle damage trigger the release of myokines such as IL-4, IL-6, LIF, and irisin from skeletal muscle, which enhance satellite cell activation and proliferation
Satellite cells fuse with existing muscle fibers to donate nuclei, supporting long-term increases in protein synthesis capacity and muscle fiber size
Training status alters the sensitivity of muscle cells to these signals — untrained individuals exhibit greater myokine release, higher satellite cell responsiveness, and stronger mTOR activation per unit of mechanical stress
Trained individuals show reduced anabolic signaling amplitude due to prior adaptations, including higher baseline myokine levels, increased androgen receptor density, and optimized neural efficiency, which diminishes the relative growth response to identical stimuli
Less supported by current evidence, but not ruled out
When someone first starts lifting weights, their muscles get stronger quickly not because they get bigger, but because their nervous system learns how to activate more muscle fibers at once — this happens before significant muscle growth occurs.
Resistance exercise increases motor unit recruitment, firing rate, and synchronization, particularly of high-threshold motor units
Corticospinal excitability improves and neural inhibition decreases, enhancing voluntary force production
These neural changes occur rapidly in untrained individuals and contribute significantly to early strength gains without proportional muscle hypertrophy
People who have trained before can pull more creatine into their muscle cells because their muscles have become better at absorbing it, which helps them retain more water and activate growth signals more effectively than beginners.
Resistance training improves insulin sensitivity and upregulates creatine transporter expression in muscle cell membranes
Trained individuals achieve higher intramuscular creatine and phosphocreatine concentrations than untrained individuals when given the same supplement
Increased cellular hydration from creatine uptake enhances mTOR signaling and protein synthesis more effectively in trained individuals
Evidence from Studies
Supporting (4)
Community contributions welcome
Creatine supplementation and resistance training: a comparison between novice and experienced lifters - a systematic review and dose-response meta-analysis
Muscle Hypertrophy, Strength, and Salivary Hormone Changes Following 9 Weeks of High- or Low-Load Resistance Training
Effect of resistance training programs differing in set structure on muscular hypertrophy and performance in untrained young men
Contradicting (0)
Community contributions welcome
Gold Standard Evidence Needed
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