How muscles grow after lifting weights
Stimuli and sensors that initiate skeletal muscle hypertrophy following resistance exercise.
Not medical advice. For informational purposes only. Always consult a healthcare professional. Terms
Muscles get bigger after you lift weights, but not while you're lifting — they grow later while resting. The body senses the pull and stress from lifting and turns on repair and growth machines. We don't fully know how the body feels that pull yet, but it might involve special proteins. Damage from lifting isn't needed to grow muscle, and chemicals made during exercise might help too — but we're not sure which ones.
Surprising Findings
Muscle damage is not essential for hypertrophy.
For decades, fitness culture equated soreness with effectiveness — this review directly challenges that belief with scientific nuance.
Practical Takeaways
You can build muscle with light weights and blood flow restriction if heavy lifting isn’t possible — e.g., during injury recovery or home workouts.
Not medical advice. For informational purposes only. Always consult a healthcare professional. Terms
Muscles get bigger after you lift weights, but not while you're lifting — they grow later while resting. The body senses the pull and stress from lifting and turns on repair and growth machines. We don't fully know how the body feels that pull yet, but it might involve special proteins. Damage from lifting isn't needed to grow muscle, and chemicals made during exercise might help too — but we're not sure which ones.
Surprising Findings
Muscle damage is not essential for hypertrophy.
For decades, fitness culture equated soreness with effectiveness — this review directly challenges that belief with scientific nuance.
Practical Takeaways
You can build muscle with light weights and blood flow restriction if heavy lifting isn’t possible — e.g., during injury recovery or home workouts.
Publication
Journal
Journal of applied physiology
Year
2019
Authors
H. Wackerhage, B. Schoenfeld, D. Hamilton, M. Lehti, J. Hulmi
Related Content
Claims (5)
Your muscles don't grow while you're lifting weights—they grow later, while you rest, because that's when your body repairs tiny tears and builds more muscle tissue using the energy and nutrients you've eaten.
When you lift weights with your blood partly blocked or using light weights, your muscles might produce chemicals that help them grow—but scientists aren’t sure exactly which chemicals or how much they really contribute yet.
When you lift weights or do resistance training, your muscles get bigger — and one big reason is that your body turns on a molecular switch (mTORC1) that tells your muscles to make more protein, though other things are also helping out.
When you lift weights, your muscles grow bigger mainly because of the physical tugging and stretching they feel — and scientists think a special protein team (filamin-C and BAG3) might be the muscle’s internal detector that tells the cell to start growing, but we still don’t fully understand how it works.
You don’t need to be sore after a workout to build muscle, but being sore might help you build a little more muscle—scientists aren’t sure how much, if at all.