Even though testosterone levels go up during a heavy workout, the muscle’s testosterone receptors don’t change in number two days later in trained men.

If you're a young, fit guy who already lifts weights, doing more weight training for 12 weeks won't change how many androgen receptors are in your muscles—but the number you started with can tell you how much bigger your muscles will get.

People who build more muscle from lifting weights might be more sensitive to testosterone because their muscles have more 'testosterone receivers' after training — but scientists aren’t completely sure yet.

When young guys who’ve never lifted weights before start training, how much their muscles grow depends a lot on what’s happening inside the muscle itself—like changes in certain proteins—not so much on hormones floating in their blood.

When men lift weights, their testosterone helps their muscles grow by turning on certain signals in the muscle cells. This hormone response can last up to two days after a workout, making muscles more responsive to testosterone during that time.

When young guys who’ve never lifted weights before train with weights for 16 weeks, those whose muscles develop more androgen receptors tend to grow bigger muscles—and this receptor increase might explain about a quarter of why some people grow stronger or bigger than others.