When guys who don’t work out lift weights, their muscles turn on a specific stress signal—no matter if they do 1 set or 5 sets. It’s like the signal just needs the weight to be lifted, not how many times they do it.

For guys who don’t lift regularly, doing weight exercises doesn’t change a specific body signal (ERK1/2) 30 minutes after working out, no matter how hard or long they train — so this signal probably isn’t what tells their muscles to grow right after a fasted workout.

When guys who don’t lift regularly do weight training, even doing more sets doesn’t change certain key muscle signals called Akt and mTOR—so those signals must already be maxed out at low workout levels, and something else is driving the bigger changes seen in other muscle signals.

When young men lift weights, if a specific protein in their muscles gets activated strongly exactly 5 hours after working out, they tend to build more muscle over the next 4 months—so this protein spike might tell us who’s going to grow the most from training.

When you lift weights that get harder or easier as you move (like with resistance bands), your body reacts more strongly in the short term—your muscles get more tired, your stress hormones spike higher, and your cells show more signs of being worked hard—compared to lifting the same weight the whole time, even after training for 20 weeks.

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.