If you’re serious about your strength training, you likely want to get the most out of your time in the gym. But if you’re like most regular joes, you don’t have hours upon hours to dedicate to working out.

If you’ve got three to four lifts you need to perform in a workout, and you’re doing those lifts for multiple sets, how long you rest between sets will determine whether you’re able to get all of your work done in your allotted gym time.

But you face a problem when it comes to taking those rests:

Rest too much between sets, and you needlessly extend your workout time.

Rest too little between sets, and you risk diminishing your performance due to fatigue.

So how long do you actually need to rest between sets so that 1) you recover enough to perform the next set, and 2) you don’t spend more time in the gym than you need to?

It depends on your fitness goals. Read on and we’ll break it down for you.

If Your Goal Is to Get Stronger: Rest ~2 Minutes

If your primary goal is to get stronger and put on muscle, you’ll want to rest long enough between sets that you’re consistently able to complete all the reps in your subsequent sets.

You could ensure that you get enough rest between sets by resting 10 minutes between them. But if you’re doing three of the major lifts (e.g., squat, bench, and deadlift) for three sets of five, that means you’d be resting for 90 minutes during your session. That’s 90 minutes of doing absolutely nothing. Ain’t nobody got time for that!

So what’s the least amount of time you can rest between sets that will still allow you to recover enough to perform your next sets?

This is actually a well-researched topic in the world of sports science.

And the consensus is about two minutes.

It all comes down to how quickly your muscles can regenerate ATP. If you remember from your high school biology class, ATP is what powers your body. Your body makes ATP in three ways; the primary way it does so while you’re lifting weights, is by recycling previously used ATP using creatine phosphate.

When you’re lifting heavy weights, for the first few reps of a set, your muscles are primarily using ATP formed from creatine phosphate you’ve already had stored in your muscles. But this power source rapidly depletes after just 10 seconds or so of an intense activity like lifting weights or sprinting.

If you feel really snappy and strong when you start a set of squats but then feel like you can barely complete the last rep, you’re experiencing creatine phosphate depletion. Your muscles are running out of creatine phosphate to power ATP production, so lifting gets harder. Studies show that when you lift until failure, your body has about 15% to 30% of the creatine phosphate levels it possesses when fully rested.

While creatine phosphate depletes pretty quickly, it can also restore itself pretty quickly. In fact, after just 30 seconds of rest, creatine phosphate levels can refresh themselves back to 50% of their full capacity. After a minute of rest, creatine phosphate levels are, on average, back to 75%; after 90 seconds of rest, they’re at 87.5%; after two minutes, they’re back to 95%.

From there, creatine phosphate goes up incrementally; to get as close to your 100% as possible, you’d likely need to rest five minutes or more.

So the question becomes: Is resting more than two minutes to get closer to 100% creatine phosphate restoration worth it?

The research suggests that the answer is typically no.

Even lifters who rest for five minutes or more don’t have significantly greater strength and muscle mass compared to those who rest for just two minutes, and most lifters will be able to complete all the reps and sets they need to do in a given workout with their creatine phosphate levels at 95%. Resting longer than the two minutes it takes to reach that level, in order to achieve 100%, has a diminishing ROI, in that you’re not getting much of an extra power boost, but are spending significantly more time in the gym.

Again, though, these are averages; whether you only need to rest two minutes or could benefit from going a little longer depends on your unique situation. You probably only need to rest two minutes between sets if you’re younger, lifting lighter weights, and/or doing single-joint lifts (like bicep curls). As you get older, the weight gets heavier,