Young men with low testosterone don't get the same muscle-building boost from weight training because their bodies don't increase the machinery needed to make new proteins — and that seems to be because they're missing testosterone.

People who get much stronger from weight training tend to make more of the cellular machinery (ribosomes) that helps build muscle, while those who don’t get as strong show little to no change in this machinery.

Lifting weights makes your muscles bigger and stronger, and this happens because your muscle cells start making more of the tiny machines that build proteins.

When you lift weights, your muscles make more of the tiny molecular machines that build proteins, which helps them grow bigger.

If untrained guys lift weights on an empty stomach, doing 5 sets of exercise really ramps up a key muscle-building signal in their cells—but just 1 set doesn’t do much, suggesting you need more than a little effort to kickstart muscle growth.

When people lift weights and their muscles get bigger, their cells make more of the tiny machines (ribosomes) that build muscle proteins — and the people who gain the most muscle tend to make the most of these machines.