3 Awesome new studies on how to build muscle in 2025

Chapters:

00:00 #1 Pre-exhaustion

05:22 My Online PT Certification Course

05:46 #2 Mind-muscle connection

09:16 #3 Lengthened partials

12:36 Outro

Transcript:

Study number one, still in preprint, compared two different ways to set up a leg day. Group number one performed the following exercises in the following order: leg curls, Romanian deadlifts, leg extensions and squats. All were performed to failure with 2 minute rest intervals. The pre-exhaust group did the same exercises, but they did the leg curls before the Romanian deadlifts and the leg extensions right before the squats, so they did isolation exercise right before the compound exercise with minimal rest in between them and then they had 2minute rest interval. Which group do you think made better gains?

After 8 weeks, the traditional group had more muscle growth across all sites. The differences were small, but they were consistent across eight measurements along the quadriceps and the hamstrings. The traditional group also made marginally better strength gains on the squat. And the traditional group got a little bit leaner, whereas the pre-exhaust group actually gained a little bit of body fat, even though there were no significant differences in nutritional intakes between the groups. And these were trained lifters, by the way.

Now, statistically, none of these differences were compelling, and scientifically, this study basically reads as a null result with no differences between groups. However, mechanistically, I would bet my money on these results panning out over a longer study with more subjects and actually becoming significant in that scenario. I think these results are real. Pre-exhausting in this manner is a bad way to set up your training program.

I believe this was originally the method pioneered by Arthur Jones on how to pre-exhaust muscle groups, and it’s still popular in some bodybuilding circles, but it has a number of negative effects on muscular tension. First – you use very short rest intervals. And originally short rest intervals were believed to be anabolic and good for muscle growth, but I comprehensively debunked this idea in one of my first big scientific publications, together with Brad Schoenfeld. We followed this up with another study showing that long rest intervals can improve muscle growth, and subsequent research also found that longer rest intervals can improve muscle protein synthesis.

Why? Because they induce more mechanical tension. If you use the same weights and you can do more repetitions because you’re rested longer, you’re increasing time under tension with the same tension as you’re using the same weights, therefore, you have a higher total aggregated stimulus for muscle growth across the session as a whole. Even worse than using short rest intervals is using short rest intervals for two exercises that are training the same muscle groups, which is exactly what you’re doing with these type of pre-exhausting. This is actually basically an agonist superset. Supersets in general can be problematic with very little rest, but agonist super sets, where you train the same muscle group with two exercises back to back, are a really bad idea.

You have to realize that after you’ve successfully trained a muscle group, it’s very difficult to keep training it effectively further, because many of the high threshold motor units have been exhausted, they have dropped out. So those motor units are done, they need recovery. And if you just keep hammering on the volume, your force output is very low because those motor units are no longer being successfully recruited. So the total amount of tension you impose on the muscle group is very low. That’s also why post failure training in general has a very poor stimulus to fatigue ratio. If you train hard to begin with, your original sets should basically get the message across for your muscles and then continuing to train them after hitting failure mostly just induces a lot more fatigue and not that much more additional muscle tension, which is the primary stimulus for muscle growth. Now in favor of the pre exhaust group, they did complete the same training program in 36% less time. That’s a very significant difference.

However, they also reported that the sessions were more effortful. I think for most individuals, if they want to shorten their sessions they’re better off just shortening their rest intervals. And research actually finds that you can get used to this as your work capacity can improve. I’m also much more of a fan of combo sets, in which you string together exercises that train unrelated muscle groups, and then you train those with at least a little bit of rest in between, enough to catch your breath. That type of organization is very time effective and doesn’t have the negative effects of agonist super sets or pre-exhaustion, however you want to call it. And then the third thing that is not ideal, I think, in this type of pre-exhaust group set up is that you train the isolation exercises before the compound exercises.

In general, this induces a weak link in the compound exercise which can reduce the volume for the other muscle groups involved. So if you train the hell out of your quads right before you do squats, this can induce a weak link and that might under stimulate your glutes, your lower back, your adductors, all the other muscle groups that are involved in the squat. And we also see this in research as a reduction in the total training load when you do isolation exercises before a compound exercise, also when you do antagonist supersets and when you use short rest intervals. And in this very study there was a 30% lower total volume load which is sets x reps x weights in the group doing the pre-exhaustion. So in general I recommend that you rest at least 90s in between sets of the same exercise, and you perform your compound exercises for any given muscle group before you do isolation exercises for that same muscle group. And I would note that electromyography research, EMG research actually perfectly predicted all these findings.

EMG research found that when you pre-exhaust a muscle group, you do not increase muscle activity in the pre-exhausted muscle group during a compound exercise. So if you do flys, for example, before bench presses, the pecs don’t actually activate more during the bench press. In fact, we see a trend towards increased activity in the triceps because they presumably have to work harder to compensate for the now weakened link of the chest. So we have a convergence here between the biomechanical rationale in terms of mechanical tension, EMG research, and now this study showing that pre-exhausting, short rest intervals and doing isolation exercises first may not be ideal.

The second new study looked at a different way to emphasize a certain muscle group in a compound exercise. Specifically, the researchers looked at the effect of concentrating on the pecs during bench presses to bench press more with your chest and less with your arms. The researchers had a group of strength trained men perform bench presses in a Smith machine to make sure this technique was standardized, while focusing either on nothing in particular or focusing on their pecs, which is, in research terms, an internal cue, and in bodybuilding terms it’s generally known as the “mind-muscle connection”. Importantly, they performed a pretty light workout in which it should be possible to change the exercise technique and muscle activity patterns, because they did only three sets of eight repetitions. That’s 50% of 1RM.

Even with such light weights these train lifters could not increase pectoralis major muscle activity by focusing on the muscle group during the exercise. There was also no effect on triceps electromyography. The workout was repeated 4x to validate these findings. Long term subscribers will know that these findings are in line with previous research that I’ve reviewed in this video, or there, or there, wherever my editor puts the link. Multiple prior studies have failed to validate the bodybuilding idea that you can emphasize a muscle group by focusing on it during the exercise.

The reason for this is that our motor cortex, the part of our brain that governs movement, is highly efficient at its job. Millions of years of evolutions have made sure that the part of our brain that governs movement is very good at coordinating movement. So when you tell it to perform a certain task it does so with great efficiency. In fact, even the best scientists in the world have struggled to make robots that are as efficient as the human brain at coordinating movement. When you perform an exercise in which the target muscle group is a prime mover, an agonist, or synergist typically, that muscle group will be activated to the full extent possible, because that is in the interest of the brain to coordinate movement with maximum force output. So when you’re doing a good chest exercise, your chest will be maximally activated if you focus simply on maximum performance. And we consistently see that focusing on anything other than maximum performance reduces force output.

So performance, how high you can jump, for example, how much you can deadlift, is impaired by thinking about anything other than jumping as high as possible or deadlifting as much as possible. Try deadlifting your 1RM while focusing on doing the movement with your quads. You won’t be able to do it. Given that trying to employ the mind-muscle connection to focus on a muscle group does not actually increase muscle activity in that muscle group, and it also doesn’t improve force output, in fact, it tends to decrease force output of the whole exercise, if it’s a compound exercise, it’s hard to see how this would possibly increase muscle growth. So I recommend that when you try to emphasize a certain muscle group you do this with your exercise selection. And you select exercises, or you perform them in such a way that that muscle group will be emphasized.

For example, if you want to emphasize your pecs during bench presses and you want to reduce activity in the triceps, use a wider grip. Now I will say that some lifters benefit from a mind-muscle connection, if you want to call it that, to improve their exercise technique. For example, when doing biceps curls, many lifters report that they have an easier time sticking to good exercise technique or not cheating when they focus on the biceps. However, there is some research that indicates that it’s generally more efficient to just tell people to focus on the good technique itself. So if, for example, you have trouble with keeping your elbows at your sides, just think about keeping your elbows at your sides. So in general, the bodybuilding idea of the mind-muscle connection doesn’t have a lot of evidence behind it, and I would focus on biomechanics primarily and good exercise selection. Good exercise technique and good exercise selection mean that you should just be able to focus on maximum performance and then you’ll get better performance and better strength gains in research, and muscle growth should be the same.

Study #3 was about lengthened partials compared to full range of motion training. Lengthened partials exploded in popularity after a study by Pedrosa et al. showed that leg extensions performed with lengthened partials outperformed full range of motion training. This study has now been reanalyzed, and the results actually don’t significantly supports lengthened partials. Researchers had a group of women do leg extensions either with a full range of motion, doing only the lengthened part, doing only the lock-out, or doing a combination of the lock-out and the lengthened part. Previously, the researchers only reported the regional differences in hypertrophy for this study. Now they looked at total muscle growth by summing all the sites together. I’m not sure why this took multiple years to do, but the results are a bit different in that lengthened partials actually didn’t significantly outperform full range of motion training at the whole muscle level. You can see the results here.

Short partials underperformed all the other groups, but there were no significant differences in total muscle growth between the other groups. There was a trend for the varied range of motion and the lengthened partials to perform the best, but this was not statistically significant, meaning, and scientifically speaking, this is weak evidence. I would also note that the female participants were untrained and not exactly training very hard. They’re trained with an RPP on the Borg scale, which is something that nobody still uses anymore, of 15/20, which was 3 to 6 sets of 7 slow repetitions at 60% of 1RM. Very submaximal, but evidently enough to induce muscle growth, so it’s not a huge limitation.

Still, it’s not representative of how serious lifters train. Overall, this new study fits with the general trend in the literature that the lengthened partial hype was probably overblown based on initial findings. We often see this in research where a first study reports a significant result and the effect size is a bit inflated. You often get that simply by statistical chance, because the likelihood of finding something significant is much greater when you have a bit of a fluke in how big the difference really is. And then when subsequent research comes out, typically you see that there’s something called regression to the mean and the effect size turns out to be a lot smaller than initially believed.

Now, I do think that lengthened partials are good, and there are multiple other studies showing that lengthened partials have some benefits, and there’s essentially no evidence, very importantly, showing that lengthened partials are worse than using any other range of motion. So the evidence overall, combined with the fact that full range of motion training generally is better than shortened partials, is very strong, that it’s very important to train muscles throughout their entire muscle length, and especially at long muscle lengths.

However, some influencers are probably going a bit overboard with this, and overall the research does not support that it’s a big difference. And importantly, I think the difference will be only noticeable for exercises that don’t train a certain muscle group well at a long muscle length to begin with. Leg extensions and calf raises, which is what most of the literature is on, really don’t stimulate the bottom position of the movement very well. For these exercises, it might make more sense to do lengthen partials then for another exercise, which is inherently very difficult at the bottom position, like a dumbbell fly or a pullover, even something like a Bayesian curl or a lat prayer, where the exercise is specifically designed, like I initially pioneered these exercises to have high resistance throughout the full range of motion. There’s little chance in that scenario, I think, that you’re going to significantly outperform by doing lengthened partials. It’s important to have high tension at long lengths. It’s not so important to only have high tension at long lengths, or to base your entire training philosophy around that, I think.

So that wraps up this week’s update on new research and exercise and nutrition science. I hope this helps you optimize your own program to make better gains. If you like this type of evidence based content, I’d be honored if you like and subscribe.