When young guys who already work out do a lot of high-volume weight training for 6 weeks, their muscles grow mostly because of fluid and non-contracting parts inside the muscle cells, not because...

Even if you do a lot of heavy weight training for 6 weeks, your muscle fibers don’t actually get more of the main building proteins—so the idea that your muscles grow by diluting those proteins with extra fluid probably isn’t right.

When young guys who haven't lifted weights before do strength training for 10 weeks, their muscle fibers grow in a way that makes them stronger, not just bigger with extra fluid. It's like building real muscle instead of just puffing it up.

In young men undergoing 12 weeks of muscle-building resistance training, taking collagen peptide supplements leads to a fivefold increase in the production of specific muscle proteins involved in contractile function, such as myosin and Z-disk components, compared to those taking a placebo.

Even though muscles get bigger after 10 weeks of weightlifting, the individual muscle fibers don’t necessarily get thicker — the growth might come from how the fibers are arranged, not from each one swelling up.

After six weeks of intense weight training, the proportions of two key muscle proteins—myosin heavy chain and actin—remain unchanged in the thigh muscles of trained young men.