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.

Even if you lift heavy or light weights for 12 weeks, your body’s short-term hormone spike after each workout doesn’t change—and that means those hormone surges probably aren’t why your muscles get bigger or stronger over time.

When young men lift weights, their hormone levels spike right after, but those spikes don’t tell us who’s going to get stronger or bigger — some people grow a lot even with small hormone changes, so something else must be behind why people respond differently.

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 short-term blip, not a long-term problem.

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.

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.