This is how long to rest between sets for max muscle

Chapters:

00:00 Intro

00:07 New study

01:27 The new science of rest intervals

06:31 Rest-pause training

07:02 Time-efficiency

08:16 Practical implications

Transcript:

How long should you rest in between your sets for maximum muscle growth? A new study provides us with answers.

The researchers had a group of men train their legs with two different rest intervals. One leg trained with shorter rest intervals and the other leg trained with longer rest intervals. Both legs performed leg extensions with 10RM loads. The leg resting longer performed 3 to 4 sets to failure with 2 minute rest intervals. The other leg only rested 20s in between their sets, and they did as many sets as needed to get the same number of repetitions as the other leg. So both legs in the end use the same load and perform the same total number of repetitions but with vastly different rest intervals.

After 10 weeks there were no significant differences in muscle growth in any of the heads of the quads as assessed by gold standard magnetic resonance imaging – MRI. Strength gains were also nearly identical at 42%. It might sound crazy 42% strength in ten weeks, but these were untrained individuals. And these days it’s popular to completely disregard a study on untrained individuals. In reality, if you look at the scientific research, it’s very rare that findings on untrained individuals do not extrapolate at all to trained individuals. Most principles of base physiology are very much the same in untrained and trained individuals. In my view, it’s actually surprising how few interaction effects there are with training status.

Trained individuals only differ from untrained individuals in a few established ways, and rest intervals so far are not one of them. The general principle at play here is that it’s the total volume that drives muscle growth and not rest intervals. For example, if we contrast this study with one of our studies, which was on trained individuals, we found that three minute rest intervals resulted in more muscle growth and higher strength gains than one minute rest intervals. The crucial difference between the new study and our study is that in the new study they equated the repetition volume between the legs, whereas in our study, we equated the number of sets, which is more representative of what serious lifters want to know. If I’m performing a certain number of sets, how long should I resting between my sets and how does this influence muscle growth?

If you’re not equating for repetitions it seems that longer rest intervals result in more muscle hypertrophy and more strength development. This makes sense in that you rest longer, your muscles can recover, you can produce more force, more time under tension, and therefore you get a greater growth stimulus in your next set. However, this line of thinking completely contrasts with how bodybuilders and even scientists used to think about rest intervals. The old consensus, in fact, was that shorter rest intervals are better for muscle hypertrophy, whereas longer rest intervals are better for strength. The idea was that shorter rest intervals were better for muscle hypertrophy because of metabolic stress and in particular, the hormonal changes that they evoked. But we now know that these hormonal changes and metabolic stress don’t correlate with muscle hypertrophy, and they are more metabolic rather than anabolic. So they are therefore energy substrate release, And they are two transient, to short lived and too small to really affect muscle hypertrophy. I extensively reviewed and critiqued the old line of thinking in one of my previous reviews on rest intervals for muscle hypertrophy.

My view is that we can understand the effects of rest intervals very well simply by looking at mechanical tension on the muscle. Mechanical tension is well-established to be the primary, perhaps the sole driver of muscle hypertrophy. Effectively, muscle is just a slab of meat, and the meat grows when you put tension on it. The amount of tension is principally governed by how much load is on the bar, how much weight you have to move. Because mechanical tension, most people can’t define it, but it’s the internal force output in the muscle, and this correlates with the load on the bar. So given a certain weight on the bar and a certain time under tension we have a decent idea of the integral of time under tension, which is basically the area under the curve of the tension that you get and how long you get that tension. That area under the curve here is essentially a good proxy for the amount of muscle growth that you are stimulating. It’s the growth signal, the growth stimulus.

Now if we roughly assume that a given load corresponds to a given level of mechanical tension in the muscle or else equal, then longer rest intervals allow you to perform more repetitions, thereby extending the time under tension and the duration of the set. Note the time under tension here is different from repetition tempo, because with repetition tempo actually you often don’t change the total time under tension. If you do shorter repetitions you cannot do as many repetitions, so you end up with a similar time under tension in many cases. That’s why time under tension does not matter from the perspective of repetition tempo, but it does matter if we think of it more in terms of volume, the total training volume, in terms of repetitions and sets.

That’s what we see in these studies where if you don’t equate sets you rest longer between your sets, you have more time under tension because you have a given weight, the same weight, and now you can perform more repetitions with that. That is more time under tension, more growth stimulus. However, if we equate the repetitions as in the new study, then we no longer see this.

The idea that rest intervals per se are largely irrelevant for muscle hypertrophy, and it’s the total repetition volume that matters, because that’s what determines the total tension stimulus on the muscle is illustrated very well by a previous study by Longo et al. In this study, the researchers had four groups a short rest interval group, a long rest interval group, and then also two groups with short and long rest intervals that equated the volume to the other group. And here you could see very well in the data that both groups that ended up with a high total repetition volume, regardless of whether they used long rest intervals or because they added more sets with short rest intervals, got more hypertrophy than the groups that used long or short rest intervals, and ended up with a lower repetition volume. So resting longer typically results in more muscle hypertrophy if it increases your total repetition volume. Short rest intervals reduce muscle hypertrophy if they reduce your repetition volume. But if you do more sets to compensate, then you can get the same growth stimulus. And if you use long rest intervals but you don’t take advantage of it and you don’t do more repetitions, then you don’t gain more muscle.

These findings fit perfectly with the Henselmans hypertrophy model that I put forth in a previous video. Very simply put: You can think of the Stimulus for muscle growth as determined by your Tension multiplied by time under tension. So if you can keep the tension the same, this is important because you’re not changing the weight in this case, and you increase the time under tension then you can stimulate more muscle hypertrophy. And rest intervals are one way to achieve this. Long rest intervals mean more repetitions is more time under tension, and we see in research there you get more anabolic signaling, more muscle protein synthesis and in longer term study, more muscle hypertrophy and also strength development. However, you can get the equivalent gains by resting shorter and just doing more sets to get that increase in total time under tension.

The new study adds to this view and shows that this is possible even with 20s rest intervals, which is essentially rest-pause training if you think about it. This means that for advanced training techniques like myo reps and rest-pause training we can likely approximate the total growth stimulus very well by how many repetitions you’re doing. In that sense, it’s a little disheartening, perhaps with rest-pause training that you probably still have to perform the same total number of repetitions as you would otherwise do to get the same growth stimulus. But it makes sense because you need to get the same time under tension multiplied by tension. However, if we look at it from a time efficiency perspective, actually the short rest intervals are much more time efficient. Because if we look at the new study, they had to perform almost double the number of sets, approximately six sets versus three sets in the short rest interval group to get the same number of repetitions as with the longer rest intervals. But they still managed to do this in less than half the time in approximately three minutes, versus seven minutes.

So if we take the view that all that matters is just how many repetitions you’re getting in with a given weight and you have to be somewhat close to failure, then time efficiency wise, short rest intervals are actually a much better way to go about this, and you can actually perform this in your own workouts if you want to save time. You know how many reps you do with, say, your planed number of sets, three sets, you see that you normally do like 12, 10, 8 repetitions, meaning you get about 20 repetitions in total for that exercise, then what you can do is just get to 20 repetitions as fast as possible. And this is probably achieved by doing once set very close to failure or to failure, and then performing shorter sets until you get those 20 repetitions.

This is effectively the idea behind myo reps popularized by Borge Fagerli, and it’s very, very time efficient. So in that sense this study is a big validation of myo reps. However I would throw in a little caveat if you want to take this to extremes. If you are a strong, serious lifter taking your sets close to failure, I do think there are limits, especially for strength development, to how short you can rest just by getting in the same total volume. Because mechanistically we know that after a set, especially one to failure, certain motor units, especially the higher threshold motor units, which have more of the type II muscle fibers that have the most growth potential, they essentially drop out. And it can take 3 to 5 minutes for energy systems like the ATP-CP system with creatine phosphate to fully resynthesize energy stores.

If you are limited by energy production and certain motor units are not yet recruited yet in the next set, then that should limit muscle hypertrophy. Even if you are getting a decent level of total tension it might leave the higher threshold motor units under stimulated. So there are probably some limits to this. But very broadly speaking you can say that really the more important thing by far is just total repetition volume and rest intervals themselves are at best slightly relevant. But perhaps even completely irrelevant as long as you’re getting a certain amount of tension multiplied by a certain time under tension, that really is the primary growth stimulus. And this conclusion has massive implications for program design because it means that theoretically you cannot set rest intervals and training volume independently.

I know that many people online, they want to know what is the best number of sets, what is the best exercise, what is the best rest interval to use? But you cannot answer those questions in isolation. In effect, what you want from a training program is the total growth stimulus that you’re getting. Just like from a diet, you cannot say – eat this food, not this food. What matters is the total diet that you’re getting. So just like that, with your training program, rest intervals are a key determinant to how effective your training volume is. And in this sense we also see that some of these studies on extremely high training volumes with, say, 45 sets per muscle group, that might only be necessary or only beneficial when you have short rest intervals.

In most studies, they use 90 to 120 second rest intervals, so two minutes or less, because it’s more time efficient and logistically in a lab when you have a lot of people coming in with supervision, you typically want to kind of get things going and push people through. If you just have people auto-regulate the rest intervals and they rest as long as they need, or when you totally feel fully recovered, then most people rest at least three minutes after serious sets, especially for compound exercises. So it’s likely that most people in practical training settings, most serious lifters, don’t require these extremely high training volumes because they rest longer and therefore get more repetitions in their later sets, which compensates for the fact that they do fewer sets than the groups in these studies performing 45 sets for a muscle group, but with very big drop offs and repetitions because they don’t rest as long, especially when training to failure. So you can do fewer sets, but with longer rest intervals and closer to failure, or you can do more sets with shorter rest intervals and not as close to failure, and you can get equivalent results, especially for muscle hypertrophy.

For strength development I would definitely err on the side of longer rest intervals though, because you want to maximize force output and muscle activity and these require a bit of rest in between sets. It’s not just about the mechanical tension in this case. This is why in my online courses I emphasize the importance of looking at the total training program design. There are interactions between rest intervals, set volume, and proximity to failure. Together they determine the optimal training stress.

There are multiple ways to Rome, and if you’re interested in maximizing muscle hypertrophy and really understanding how all of these concepts fit together, then I highly recommend my online course. The link is in the description. You’ll learn absolutely everything you need to know to maximize muscle hypertrophy, fat loss and strength development. But I realize that is an unsatisfactory conclusion from any of my viewers.

So I can also give you a simple version: For most people if you just auto regulate your rest intervals and you rest until you feel fully recovered for maximum performance, so you’re probably not really fully recovered because many people don’t really fully recover in one workout, you can perform your next set again. Performing your workouts this way is very practical because you don’t have to time your sets, and it also means that you probably don’t have to do the insane volumes that you see in some of these 45 set studies because your rest intervals are going to be longer than that in those studies. It’s not the most time efficient, but it’s very practical. People typically like having a bit of rest in between their sets, and it reduces the RPE of the total session. So total session RPE, which is different from the RPE of a single set, is typically lower when people rest a bit longer.

For time efficiency, though if you’re currently already training like this, what you can do is look at how many total repetitions you’re getting in your current sets with current weight, and then with that same weight or same intensity see how you can perform that number of reps in the least number of sets. This is essentially what myo reps do, and myo reps, therefore, are a really good way to save time in your workouts.

All right, I hope this helps you with your program design and gives you some options, so basically the simple version, the advanced version, and the time saving option to construct workouts more efficiently for your goals. If you like this type of evidence based content, I’d be honored if you like and subscribe.