When people lift weights at a high effort level, their untrained muscles build more protein quickly, but their already-trained muscles don't get the same boost, even if they do more work.

When young men who haven't trained before do one-arm exercises for eight weeks, their resting muscle building speed goes up by almost half in that arm, but the part that builds muscle fibers stays the same, showing different parts of muscle react differently to exercise.

Lifting weights at a challenging level makes your muscles build more protein, and this boost happens just as much in arms or legs that are used to exercising as in ones that aren't.

When you do strength training, your body gets better at building the proteins that make muscles strong, while cutting back on making other less important proteins. It's like your body learns to focus on what really matters for muscle power.

When people who already work out regularly train more often, it might help them build more muscle. Since their muscles don't respond as strongly to each individual session, working out more frequently keeps their muscle-building processes active for longer periods.

Eating protein after working out only increases the building of connective tissue in muscles for about 4 hours - after that, the building rate goes back to normal.