Even if your muscles don’t get much bigger from lifting weights, your body still improves how it uses energy, like making your muscles better at burning fuel efficiently.

If older people who didn’t get stronger from doing just one set of weight exercises start doing four sets instead, they’ll likely grow bigger muscles in their thighs after 10 weeks of working out twice a week.

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.

People’s muscles before they start lifting weights already have different gene activity patterns, and those patterns seem to predict how much their muscles will grow after training.

Lifting weights helps people build bigger, stronger muscles, probably because it makes their muscles produce more protein and release helpful signaling molecules that help them grow and work better.

When older men get stronger quickly at the start of weight training, it’s often just because they’re learning how to lift better—not because their muscles are growing or getting stronger for real. So, early gains don’t mean they’ll keep getting stronger over time.