The Muscle Building Myth Everyone Fell For (NEW Study)

I just spent over $40,000 on this study to prove everyone wrong because recently the entire fitness community has become obsessed with the same thing. — I'm all on the stretch wave these days. Ultra focus off a stretch — and now you get a much bigger stretch here. — The theory is if you modify an exercise to stretch your muscle more or challenge it in the stretch, it now becomes S tier for growth. And to be fair, I said the exact same thing and for good reason. as we had dozens of studies supporting this idea. But despite all this research, the evidence back in our claims, it has some massive holes in it. And there's a real chance this obsession with the stretch is completely overblown. So to find out, I assembled an elite research team, brought in custom machines, and spent an entire year running one of the most comprehensive studies ever done. All to answer one simple question. Is the stretch really the key to building more muscle? And the result we found didn't just shock me. — Do these findings change your thoughts on some of the exercises that you may have thought better for growth. — Kind of. Yeah, I think — before we get there, it's important to understand what the stretch actually means and where all the hype came from. So, we've actually known about the benefits of stretching a muscle for growth since the 1970s. It started when researchers hung weights from the wings of chickens to stretch their lat muscles. An odd experiment, I'll admit, but just from this stretch alone, the chickens lats grew by 170%. Then in humans, they tried something similar, extreme loaded stretching. They tested this on the chest and even on the calves, where my friend Dr. Eric Helms wore an intense stretching calf boot for an hour a day. Both muscle groups saw almost as much growth from loaded stretching as you would expect from normal strength training. This gave researchers a clue that something about stretching the muscle seems to be a powerful signal for growth. So they wondered, how can we transfer these odd stretch benefits into normal training? One way they tested this was by comparing tricep push downs to overhead tricep extensions, which places the long head of your triceps into a deeper stretch. That deep stretch led to 1 4 times the growth. Remember this exercise because later on you'll learn why exactly it works so well for the triceps. But what if you didn't just stretch the muscle more, but actually challenge the muscle most when it's stretched? To test this, researchers would have people hold a max contraction with their legs fixed at different angles. when their leg was more bent, which challenges the quads in a more stretched position, their muscles would grow up to twice as much as when their leg was straighter and the quads not as stretched. But they didn't stop there. They tested it again using real reps, comparing the bottom half of a leg extension to the top half. And again, the version that hit the stretch harder led to way more growth. And that is when the trend exploded. Suddenly, stretch focus training became the answer to everything. faster gains, S2 results, weird optimized exercises that look nothing like what we used to do. But the deeper I looked, the more I realized there were three serious gaps in the research that no one was really talking about. First of all, almost every study showing that training in the stretch helps muscle growth has only been done on the biceps, quads, or calves because they're easier and cheaper to test. But other muscles don't stretch the same way, and some are built completely differently. One muscle in particular research has shown gets a crazy growth response from the stretch that we don't see in others. I'll reveal what that muscle is at the end, plus how to train it. But second, many of these studies, they compare totally different exercises. For example, preacher curls versus incline curls. Preacher curls hit the biceps hardest in the stretch, and they did show more growth in one study, but they also lock your arm in place, making it harder to achieve. So, was the extra growth from the stretch challenge or the extra stability or both? And third, this one's a bit more technical, but most studies measure growth using ultrasound. It's fast, it's cheap, and I've used it myself in past videos, but it has limits. Not every muscle can be accurately measured with ultrasound, and for the ones that can, it only provides a snapshot of a muscle by looking at the thickness, often at just one point. This is an issue, especially with stretch research, as muscles don't grow evenly from top to bottom. So, while one region might look like it grew more, it could have grown less in other areas. Now, these issues sound small, but once you see how they played out in our study, you'll understand why they matter so much. But now comes the hard part. How do you actually design a study that fills in these three gaps? First, I reached out to my local university and put together a research team. And we also collaborated with some of the smartest minds in the field, including Brett Contraras and Cassm Hansen to build the plan. The goal to test muscles that rarely ever get studied and to see

if the benefits of the stretch, which worked for the quads, calves, and biceps would hold up when applied to muscles like the chest, glutes, side delts, and rear delts. And because these are muscles that can be measured accurately using ultrasound, we needed to get the gold standard, MRI. So MRI gives us a full 3D model of each muscle, and it's incredibly precise, but it's also insanely expensive, costing roughly $1,000 an hour. For our study, we needed at least 20 hours. And well, you can do the math. This was a huge chunk of our budget, and I'm incredibly grateful that Brett Contraras, also known as the glute guy, stepped in to graciously help us fund it, which left us with just one more problem left to solve. So, we wanted to test if an exercise that's hardest in the stretch actually builds more muscle compared to if we could somehow make that same exercise hardest in the squeeze. If the stretch grew more muscle, it would validate every exercise swap and adjustment science-based lifters have been recommending for years. But if the squeeze built more muscle, that would mean all those recommendations weren't necessary or even worse, were actually hurting your gains. But how exactly do you take the same exercise and make it harder in the stretch for one group and then harder in the squeeze for another? And that is where our equipment became the key to the whole experiment. Prime Fitness USA, they provided us with three custom machines for lateral raises, hip extensions, pec flies, and reverse flies. But here is a really cool part. So with a simple turn of a knob, we could change the resistance profile instantly. With this knob, we can make pec flies brutally hard in the beginning when the chest is stretched or hardest at the end when it's fully squeezed. But aside from that one change, the exercise and the range of motion stays exactly the same. Meaning the only thing that could affect growth was whether the movement was hardest in the stretch or in the squeeze. It was the cleanest test of stretch versus squeeze ever done. From here, we recruited 20 subjects, both men and women. And while 20 people might sound like a small sample size, we use a unique design that controls genetics, diet, and all other individual variables that usually muddy the results. It's called a within subjects design, which splits each person in half. One side of their body did the stretch focus training, and the other side did the squeeze focus training. This now makes our 20 subject study statistically much stronger than a regular study with well over 40 subjects. And my hypothesis, as well as the hypothesis from the rest of our research team, was that the stretch side would no doubt outperform the squeeze side. — Pressure on the heel, nice and tall, and then we're sweeping that leg down and back. Good. Controlling up. — However, when I got to talk to some of our test subjects, most of them were predicting the exact opposite. I think my left leg, which is the one that gets harder near the end, is going to more just cuz it's harder. — JJ's my friend and I enrolled him in the study. And uh I mean like I ever since like two weeks ago, I just kind of noticed he was getting some wicked gains on his shoulders. — Is one shoulder noticeably bigger than the other? — That I don't know that I don't know. But um — definitely there's been some size growth. We'll see. We'll see if the MRI is done. — Interesting. But to ensure no one's bias would actually influence the results, we blended everything. The MRI analyst nor our statistician knew which side was which. And I didn't see any results until the stats were finalized. Now, analyzing the MRI data alone took Adam Jones, our head researcher, over 200 hours, as every single image had to be manually outlined and measured. But our adherence was insanely high, 97%. Out of 400 possible workouts, 388 were attended. And as a result, most people's muscles grew by around 20% bigger, which is excellent for just 10 weeks. And it makes it more likely that if there was a difference favoring one side, we'd be able to catch it. And the results we found didn't just challenge my views, but also that of my fellow science nerd, Jeff Nippert, who had some interesting thoughts when I showed him the results. But we'll get to that in a bit. So, which side grew more? Stretch or squeeze? Now, before I say the winner, I want you to take a guess which side won. No cheating by skipping ahead. Stretch or squeeze. Just lock in your answer. Okay. So, after $40,000 spent and a year of hard work, our results were chest, same growth, side delts, same growth, rear delts, same growth, and glutes same growth. Every single muscle grew the exact same amount on both sides. There weren't even trends suggesting that one side performed better. We even reported growth at three points along each muscle to see if maybe

the stretch affected certain regions more as well as one total volume comparison. Still same growth. I was honestly shocked. But when I dug deeper into the data, which I'll show you in a second, it actually explains why so many of us were misled. Which leads me to our final question. What do these results mean? And what are the stretch focus exercises that actually matter? Okay, so after comparing data from our study against past research in the field, I noticed a few things. First, when it comes to the stretch everybody keeps talking about, it's not all one thing. In fact, I would say it's actually three different ideas that just get mashed together. The first of which is what I'm going to call the degree of stretch. So, not all muscles are built to stretch the same way. Some of them, which are mainly found in your hamstrings, quads, calves, and triceps, they're barticulate. And that just means they cross two joints, which lets them stretch further than most other muscles. And here's the important part. Studies consistently show that exercises that stretch these muscles more grow them faster. And because these muscles are also some of the cheapest and easiest to test, it makes sense why so many studies found stretch training to be more effective. Now, the second way the stretch gets applied to training is through basic range of motion. So, how deep you go on each rep. And again, studies find that the stretch position, often the bottom part of a movement, tends to be the most important part for growth. So, if you're simply not going deep enough on an exercise to reach that point, that will most definitely limit your gains. And again, nothing in our study contradicts these findings as both our stretch group and our squeeze group were still completing a full range of motion each rep. What our study tested was the third and most misunderstood piece of the stretch compensation, the resistance profile. Does making an exercise harder in the stretch actually lead to more growth? And from our study, the answer is a clear no. As long as the exercise takes your muscle through a full range of motion and there's at least some tension in the stretch, it doesn't seem to matter if the hardest part is at the bottom or the top. And these findings, they actually line up with another brand new study published just this year that compared cable lateral raises to dumbbell lateral raises. Even though one of them was designed to be hardest at the bottom in the stretch and the other hardest at the top during the squeeze, both led to similar shoulder growth. Now, here is where things get even cooler. Some muscles, they do still respond differently to the stretch, and I'll show you which ones in a second, but I first want to cover some of the limitations of our study. For one, we used untrained subjects. Now, some argue that beginners grow from almost anything. So, they're not ideal for detecting smaller differences between training methods. And while that is a fair point, it's also worth noting that most research in this area does use untrained participants and still finds clear differences between the groups. But I do think that for well-trained lifters like myself, doing something new can often spark growth. And I actually think this happened to me after years of only doing dumbbell lateral raises, which challenged my shoulders hardest in the squeeze. Switching to cable lateral raises at hip height to make it harder during the stretch seemed to grow my shoulders much faster. Now whether it was a new stretch challenge that I wasn't used to or simply me just enjoying the exercise more and pushing harder, it worked. And the good news is that this isn't an eitheror situation. You can do both in your workouts like I do because we still don't know if combining both stretch and squeezebased exercises leads to better long-term results. And lastly, although we tested muscles that had rarely been studied before, there are still others that may have responded differently. Take the calves for example. They seem to be one of the few muscle groups that respond extremely well to training in the stretch. So much so that one study even found that doing just half reps at the bottom in that stretch led to more growth than doing full range of motion reps. But here's what I think is actually really encouraging. Even though this is just one study, if future research on more muscles continues to align with what we found, it means something important. As long as you're training hard and you're not cutting your range of motion short, there's actually a wide range of exercises that can be very effective for growth. Hip thrust, for example, can be just as good as squats for your glutes. Reverse dumbbell flies can be just as good as cables. and chest flies might just build your chest as much as the bench press, which is all great to know if you're working around an injury, limited on equipment, or just want something that's easier to recover from. The exceptions, however, are these handful of barticulate muscles that do actually benefit from the extra stretch. And these are the exercises that researchers found grows them best. So, I would highly recommend making sure these are in your routine. The lats also might be another exception, but we just don't have the data yet. But that's just my opinion. And I want to talk to someone who's also been a huge advocate of the

stretch to see if any of our research changes his recommendations. — Yo yo. — Okay. So, now that you have actually had a chance to read the results, I'm really curious to hear like what you think. — Yeah, it looks amazing, by the way. Like I Oh, man. I didn't realize you were using MRI for it. I think it's a really important um uh area that you've helped kind of fill in. Do these findings change your I guess your thoughts on some of the exercises that you may have thought are like better for growth — kind of. Um yeah, I mean I think with the pecs that's probably the one that like I'm like ah okay well now you know what uh you don't get a little bit of extra range of motion uh by doing the bench press like nah as long as you're training hard and you know doing enough sets maybe it doesn't matter so much. So that's a cool finding. I think like my takeaway based on this new study is that like there there's just flexibility, right? I think this is like h it's like kind of gets to like a deeper point about what science-based training should be and how it should be communicated. I don't think there's anyone in the evidence-based field who would be like, "No, no, no. " Like the stretch is literally number one. Like more important than training hard, more important than how much volume you do, more important than like controlling the weight and progressive overload and consistency and all this stuff. Like that's not a take. We kind of have like a lot of the puzzle pieces in place when it comes to those like fundamental variables. And these are just like the final few pieces that were like trying to fit in. — Yeah. And that was one of the goals with our study, too. Now, I know some people are going to watch this and say science-based lifters always flip-flopping their stance. But nothing in our study disproves the past research. It simply gave us more clarity as to where the stretch actually matters and where it probably doesn't. And that is what science is all about. Building on what we have, questioning what we don't and refining our stance as we learn more. But I will admit this whole experience has definitely taught me to be more cautious about how I interpret and communicate new findates. And actually this study is just the beginning. We have already started our next study which is the first of its kind. I'm going to give you a sneak peek of that in a little bit because when I first started this channel 7 years ago, one of my biggest dreams was to run studies just like this. And now because of your support and everyone who has joined our Built with Science app, that dream is real. Now, we take a portion of the app's profits and we put it directly into funding studies just like this. And in return, you get your own science-based pocket coach that builds your workouts, tracks your progress, and helps you train and diet smarter. All based on the latest research. That is exactly why we're running our first ever MRI study on back growth, comparing rows versus pull downs, so that when you follow the app's workout routines, you know that you're doing what's truly most effective. Tons of our users have also been loving the new AI version of me, which is trained with all of my knowledge, our dieticians, and the latest science. It looks at your strength data and gives you personalized coaching whenever you need it. And as a result, our members have been getting some insane transformations. And the best part is you can try it completely free for two weeks. Plus, for Black Friday, if you end up joining, you'll get a special 20% off valid only from right now until December 1st. Just head over to builtwithscience. com or scan this QR code right here. And if you're watching this after the deadline, I've included another code in the description just to make sure you're still going to have some perks. And if you do want to read the preprint of our study, I'm going to leave a link in the description box down below.