No matter which way you measure muscle growth—whether you count all non-fat weight, lean tissue, or just skeletal muscle—you get pretty much the same result when guys lift weights. So, you can use any of these methods and still track muscle gain accurately.

If you're a guy between 18 and 40 and you start lifting weights, whether you're new to it or have been doing it for years, you probably won't gain much more muscle just because you're experienced—but the people who’ve trained the longest (4+ years) still tend to gain the most muscle, so experience doesn’t always make a clear difference.

Getting stronger from lifting weights doesn’t always mean your muscles are getting bigger—and vice versa. Strength and size don’t go hand in hand.

If you're a young guy lifting weights more often each week, you'll likely get stronger faster—but that doesn't mean your muscles will get noticeably bigger.

If you want to get stronger, doing your workouts more often helps—more than if you just want to get bigger muscles.

If you lift weights the same amount and with the same effort, whether you use free weights or machines, you’ll grow your muscles just as much—neither one is better than the other for building muscle size.