When you do resistance training with changing resistance (like bands or machines that get harder at different points), your body sends out quick chemical signals—like ERK1/2 and hormones—that seem to help you feel less tired over time, possibly making you more endurance-ready in the long run.

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.

When trained guys do lots of reps, they feel more tired, weaker longer, and more stressed than when they do fewer heavy reps — even though their muscles are damaged about the same.

For people who already lift weights, it doesn’t matter much if you rest 30 seconds or 2.5 minutes between sets of light weights — you get the same muscle growth and strength gains either way.

If you train with weights that change resistance throughout the movement (like using bands or machines that adjust), you can do more reps and lift more total weight before getting tired than if you use the same weight the whole time — and after 20 weeks, this difference is pretty big.

Whether you rest a short or long time between light weightlifting sets, your body releases about the same amount of growth-related hormones right after the workout.