Honestly, every gym and weight room should include preschool manners charts posted on the walls, because it often seems like basic human decorum goes out the window the second people are allowed to show off their strength. For example: Keep your hands to yourself. Use polite words. And, most importantly, wait your turn.
You may have seen some people obsessively check their watch or hover around weight machines while they wait to use them. It can be very annoying, because it makes you feel like you're somehow in the way or going too slow. But there actually is a reason why people time their rest periods between exercise sets — and it's not as rude as it seems.
Rest is important, not just so you can catch your breath and be able to do more exercises, but also because it allows your muscles to recover. To get really scientific about this, we know that your muscles get energy for resistance training from a substance called creatine phosphate. After a set of exercises, it can take up to a minute for the levels of creatine phosphate to get back to normal. So, you gotta wait it out!
As a broad rule, the amount of time you should rest between exercises or sets depends on the amount of weight you're lifting and what your overall goal is, according to the American Council on Exercise. We all have very different goals when it comes to working out, but for most people looking to improve their muscular fitness, it's best to rest for 30 to 90 seconds between sets of an exercise. You should feel energized to get after your next set, but not so relaxed that your heart rate drops and your body cools down.
For people with more specific goals, then timing is more important. Maybe you're trying to build muscular endurance, because you're a cyclist or dancer, for example. In that case, you'd want to keep your rest time less than 30 seconds between sets, to condition your muscles to keep working throughout long workouts. On the flip side, if you're lifting heavier weights in order to build strength and power, then you should wait two to five minutes between sets. Powerlifters might wait around for minutes before they perform another exercise again, while bodybuilders tend to lift heavy weights and rest for 30 to 90 seconds.
Keep in mind that these are just general guidelines developed by exercise scientists that trainers use to make sure that their clients are getting the most out of their workouts. But you have to do what makes the most sense for you, your body, and your workout. If you feel like you're rushing through a strength-training circuit, it's worth it to give yourself time to rest so you don't overdo it.
In other words, if someone in your weight room seems to be breathing down your neck and obsessively checking their watch, they're probably just worrying about their own workout. And you should, too.