Increases in strength are mainly due to changes in how the nervous system activates muscles, while increases in muscle size are mainly due to the total amount of training performed within a...
Mechanism
Synthesis from 5 studies
You get stronger quickly because your brain and nerves learn to turn on more muscle fibers and fire them faster. Your muscles grow bigger over time only if you do enough total work—more sets and reps—because that tension tells your cells to build more contractile proteins. Load doesn't matter as...
Most probable mechanism
When you train, your brain and spinal cord get better at turning on your muscle fibers more fully and firing them faster, which makes you stronger right away. Over time, doing more sets and reps creates enough tension in your muscles to trigger signals that tell your cells to build more contractile proteins, making your muscles bigger. Strength improves first because your nervous system adapts quickly, but muscle growth takes longer and depends on how much total work you do, not how heavy the weight is.
Mechanical tension from muscle contractions activates sensory feedback from muscle spindles and Golgi tendon organs, increasing excitatory input to spinal motor neurons
Enhanced spinal motor neuron excitability increases the firing rate of already recruited motor units, elevating force production through rate coding
Sustained contractions to fatigue recruit higher-threshold motor units, achieving near-maximal muscle fiber activation regardless of load
Mechanical tension and metabolic stress activate mechanosensitive pathways including integrins and focal adhesion kinases, triggering mTORC1 signaling
mTORC1 activation phosphorylates downstream targets such as p70S6K, enhancing translational efficiency and increasing myofibrillar protein synthesis rates
Repeated daily increases in protein synthesis, when supported by adequate nutrition, lead to net accumulation of actin and myosin filaments within muscle fibers
Accumulated contractile proteins increase muscle fiber cross-sectional area, resulting in measurable hypertrophy
Chronic training raises the torque threshold required to recruit and de-recruit motor units, improving neuromuscular efficiency and force gradation
Evidence from Studies
Supporting (5)
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Resistance Training Volume Enhances Muscle Hypertrophy, but Not Strength in Postmenopausal Women: A Randomized Controlled Trial
Resistance exercise load does not determine training-mediated hypertrophic gains in young men.
Velocity Specific Adaptations to Three Widely Used Strength Training Methods: A Randomized Controlled Trial.
Changes in agonist neural drive, hypertrophy and pre-training strength all contribute to the individual strength gains after resistance training
Contradicting (0)
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