How long should you rest between each set you perform? This is a question that many people ask, and there is a lot of confusion and misinformation floating around in regards to the answer. Some people swear by shorter rest times, stating that it's better for bodybuilding styled training, others, especially powerlifters, say you should rest for as long as you need to be ready for your next set. So, who's right? Are there benefits to shorter rest periods or should you be resting a bit longer between sets? Let's dive in.
Rest periods used by different types of athletes
Old school bodybuilders had a heavy focus on shorter rest periods. By using shorter rest periods, they were able to keep their muscles fatigued, maintain "the burn" and maintain pumps in their muscles (increased bloodblow). This was thought to cause more hypertrophy because the muscle always felt highly stimulated and much more fatigued overall. Because of this, they avoided very long rest periods that allowed the burning sensation in their muscles to subside and their pumps to fade, fearing this would reduce hypertrophy.
On the other hand, strength athletes have always used longer rest periods, because it allows the athlete to be prepared to give their maximum performance each set, which is extremely important for strength showcasing and strength development. When inadequate rest periods are taken, performance will take a large hit, which ultimately means less weight used or reps performed and a weaker training stimulus.
Does inadequate rest affect muscle growth?
It's pretty clear that inadequate rest periods will negatively impact strength performance on subsequent sets because it is immediately evident when it happens, but what about for muscle growth, a process that takes much longer to notice? How do short rest periods affect muscle growth?
Recent research is starting to paint a clear picture. For example, a new study  shows that when performance drops off due to inadequate rest, each set performed this way can build as much as 50% less muscle.
This is pretty eye opening and highlights the importance between performance and hypertrophy. For maximal muscle growth, each set should be done when the targeted muscle has received adequate rest to perform at it's maximal capacity.
This means that the old school bodybuilders didn't have it right. However, the reason they were able to build so much muscle despite this is for multiple reasons. One, many of them were on anabolic steroids and two, the reduction in per set hypertrophy can be offset by doing more total sets. So while they weren't getting as much per set stimulus that they could have gotten, they still accumulated a lot of stimulus due to performing a large amount of sets.
So how long should you rest then?
Rest times are highly individualistic, but the idea is that you should rest long enough so that you feel ready to give the next set your all and not be limited by a lack of rest. This will commonly work out to be 3-5 minutes for larger compound movements such as the Bench, Squat and Deadlift and around 1-2 minutes for smaller isolation movements.
By resting adequately, you can ensure that you're able to give each set the performance it needs to produce as much training stimulus as possible. Resting an extra minute or two before you move on to another set is a small price to pay for the added benefits you'll gain from doing so.
Some people, however, are able to get away with shorter rest periods than mentioned above. To find out how long you should be resting, simply try different rest periods and compare your performance with each. If you don't see any rep drop offs from shorter rest periods and feel like you're able to give it your all, then by all means, use the shorter rest periods. Don't use long rest periods than you actually need or you may actually be wasting time trying to hit some arbitrary amount of rest that doesn't exactly fit your individual body.
Alternative time saving options
Since you may no longer want to use shorter rest periods as a time saving tool, you may be wondering then, is there any way to get through a workout faster without reducing the overall stimulus of the workout? Luckily, there is. Better alternatives do exist, which either don't interfere with the hypertrophic response or do so very minimally. These are super sets and giant sets.
Supersets are when you perform one exercise immediately after another with no rest in between. This is best done with different muscles groups so there is minimal overlap with the muscles being used for each exercise. One example would be doing barbell curls immediately followed by tricep pushdowns. The barbell curls won't affect the tricep pushdowns. This will allow you to quickly finish one set of two different exercises, increasing time efficiency with minimal downside.
Giant sets are very similar to super sets, except they involve more than two exercises. So you'll be performing three or more exercises in a row without rest in between each. Preferably this will also be with exercises that do not hit the same muscles. Giant sets should be reserved for times when it's really important that you get out of the gym faster, as they can lead to what we call "junk sets". Junk sets are sets that are not taken close enough to failure to produce an adequate training stimulus. This is common with giant sets because the first exercise or two that you perform can tire you out before you get to the last exercise, increasing the chance that you end a set prematurely due to fatigue.
Train Closer To Failure
It's common knowledge now that the more volume you do, the more progress you can stimulate. However, let's not forget about another very important factor that can affect how strong of a stimulus you get from training: Intensity. The closer to failure you take a set, the stronger the training stimulus. When you're strapped for time and have to give up on finishing some of your sets, it may be a good idea to allow your RIR (Reps in Reserve) to decrease slightly and maybe even take a single set to failure to make up for the lack of volume. When volume is forced to decrease, you might as well increase intensity to compensate.
Here's an example: If you were planning on doing 5 sets of bench press with an RIR of 3, but you end up having to cut your workout short and know you can only finish three sets, you could take those three sets a bit closer to failure and use an RIR of 2 or 1. You could also leave the first two sets at an RIR of 3 and take your last set to failure as well. There are many ways this can be applied to your benefit, just make sure not to over do it on the intensity and cause recovery problems.