How Long Should You Rest Between Sets in Your Workout?

Whether you're lifting weights or doing a HIIT workout, what you ​don't​ do is just as important as the moves you choose. That means putting rests between each set, and not just as a way to catch your breath. Here's what you should know about building this essential component into every workout.

Knowing the "why" behind rests can be helpful when planning your workout, and it comes down to muscle fuel systems. Here's a quick breakdown.

The energy that comes from food is converted into a usable form called adenosine triphosphate, or ATP. This is utilized for all cellular functions, and a small amount is stored in the muscles. Because not much is stashed that way, it must be constantly resynthesized, which occurs with three energy systems: phosphagen, anaerobic glycolysis and aerobic glycolysis.

Muscle contraction relies on breakdown of ATP, and the more intense your workout, the faster you'll be depleting that stored energy. Rest will fill that tank back up, but it takes a brief pause in exercise for this to happen.

In general, it takes the body 60 seconds to reach 90 percent recovery of its ATP, and three minutes to achieve complete recovery, according to Brooke Van Paris, certified personal trainer and Life Time master trainer in Florida.

"This basically means that the longer the rest, the more ability you have to complete the subsequent sets with the same effort level as the previous one," she says.

For workouts like HIIT, Tabata and circuit training, 30 seconds is often long enough rest between sets because rests need to be shorter — between 30 to 60 seconds — to increase the "burn" in the muscles, according to Rocky Snyder, a California-based certified strength and conditioning specialist. Each set can be multiple exercises, and there's usually no rest moving from one movement to the next.

Having no rest between each exercise yields a higher fat burn effect, adds Van Paris. Keep in mind that it may take time to get to that level of intensity where you don't need to pause between moves within a set and can reserve your short rest for purely between sets.

If you feel like you're struggling to maintain proper form, Snyder suggests slowing down within a set, doing fewer reps or doing fewer exercises. Sometimes, just choosing three or four exercises per set with a 30-second rest between them and 3 sets total will be enough to build endurance and burn fat.

If you're looking to build muscle through lifting heavy and doing fewer reps and sets — as opposed to lifting lighter and doing more reps in each set — longer holds of 90 to 120 seconds are the way to go, according to Snyder. Longer rests are also preferred for explosive movements such as plyometrics (box jumps, for example ) as well as Olympic lifts and other movements that are high intensity, because this allows muscle energy to replenish before your next set.

If you're new to strength training and usually do HIIT or other cardio, this will likely feel like a long time to rest. You might get a little antsy. But power through that discomfort, because if you cut the rest short to launch into your next set, you likely won't be giving your muscles enough time to recover.

Another tip when beginning a strength program: Consider fewer sets, Snyder suggests. Doing just 1 or 2 sets of each movement, like biceps curls, and not performing them all the way to total muscle fatigue will reduce the likelihood of delayed muscle soreness but will still stimulate the muscles for future growth.

Longer rests are also a good strategy when you're coming back from injury, he adds.

"Injuries create altered movement patterns, otherwise known as compensations," he says. "Getting the body to move properly is a big goal when working with injuries. Fatigue may set in sooner than the average workout, so rest periods between sets should be a little longer to allow for that."

Particularly for a HIIT workout, it can be easy to shorten rest times even more than they already are as a way to power through your sets, but that might limit your results over time. Instead, try accurately timing your rests to make sure you're resting for the full stretch of each one.

This can be done on a phone or with a simple timer, but if you have a fitness watch that lets you preset work and rest intervals, that's even better. (Don't have one yet? Check out the best fitness trackers according to trainers.) Once you've done several workouts with predetermined rest intervals, then you can start playing around with different time frames for rest to determine what's working best for you.

"A good rule of thumb would be to rest longer for sets of high intensity," Snyder says. "If the set was easy, only rest for 20 seconds between sets. As the intensity of the set increases, the rest time should increase, too."

In terms of what to do during rest, sitting on a weight bench and scrolling social media may be tempting, but there are better options, Snyder adds. To make the most of that time, opt for gentle, active rest — such as walking around or doing a few easy stretches — because that allows for a gradual decrease in heart rate, putting less strain on the cardiovascular system.