If young guys who lift weights do intense training every day for two weeks, their morning hormone levels might dip for a bit—but they bounce back within four days after stopping, so it’s just a...

When young men lift weights for 12 weeks, their short-term spikes in testosterone and IGF-1 after workouts don’t seem to predict whether they’ll gain more muscle or get stronger.

When young men lift weights regularly for 15 weeks, their body’s immediate hormone spike after each workout stays about the same—no matter how many times they do it. It’s like their body keeps reacting the same way every time, without getting used to it.

During a tough leg workout, testosterone levels spike temporarily, but they go back to normal by the next day and don’t stay high.

When young guys who lift weights regularly do intense leg workouts for two weeks, those who gain more strength also tend to have bigger increases in their morning testosterone levels.

Even if your hormones spike a lot right after your first few workouts, that doesn’t mean you’ll grow more muscle or get stronger later on.