6 GORGEOUS new studies to help you build muscle [2025]

Chapters:

00:00 Intro

00:20 Study #1: Eccentric rep tempo

03:54 Study #2: Biceps training

04:29 Study #3: Strength vs size

06:52 Study #4: Should you wear a belt during squats?

08:27 My Online PT Course

08:54 Study #5: Lengthened partials

11:14 Study #6: Lengthened isometrics

14:04 Outro

Transcript:

A new scientific review of 32 studies concluded that more muscular men have harder erections, more libido, and higher overall sexual performance, independent of their testosterone levels. Proving once again that there is no problem in life that cannot be solved by getting more muscular. So here are 6 studies to help you get more jacked.

Study #1 is a meta-analysis of 9 studies that looked at the effect of how fast you should lower your weights for maximum muscle growth, strength development, and power gains. The eccentric, also called the negative, is usually the lowering phase of a lift, especially if you’re using a free weight. But formally an eccentric muscle contraction means that the muscle is lengthening while contracting and producing force. The researchers overall conclusion was that eccentric repetition duration, how fast you lower your weights, had no effect on muscle hypertrophy or strength development. However, slower eccentrics were worse for the development of power, as measured by gains in jump height. To develop high rate of force development you want to train explosively. Of course, training with very slow eccentrics is not an ideal way to do this in large part because you reduce the benefits of the stretch shortening cycle.

When a muscle lengthens under load a signal is sent from the brain to the muscle, in part to prevent it from tearing, to contract more forcefully. Combined with the elastic rebound that you get from muscle and other connective tissue, this is why we naturally have a short eccentric movement before we have an explosive concentric. For example, when you jump you first dip down a bit and then you jump up. When you throw a dumbbell at somebody doing biceps curls in a squat rack, you first cock and then throw. When you perform an eccentric movement very slowly, the benefits of this stretch shortening cycle dissipate over time. So you cannot be as explosive.

While slow eccentrics might not be ideal to build power they are commonly thought to be ideal for muscle hypertrophy and for bodybuilding purposes. However, it doesn’t seem to matter for the accumulated mechanical tension that the muscle develops if you do more faster repetitions or fewer slower repetitions. In the end, it’s still the same load taken to a similar proximity to failure, so there is no effect of the eccentric repetition duration on muscle hypertrophy in most research and on average, according to this meta analysis. The effect size was almost exactly zero, in fact.

However, I will caveat this by saying that most studies look at at least a somewhat controlled eccentric duration of at least a second or more compared to an eccentric duration of multiple seconds. I think when you do a very fast eccentric and a few studies have looked at this somewhat, you will get worse gains because there needs to be an eccentric muscle action, which is very important for muscle hypertrophy, that’s when a lot of force generation can take place, and there are some benefits with passive force production and the spring loading of the titin filament for example. If you don’t have that eccentric muscle action at all, meaning that you’re just dive bombing down during a squat or a chin up and you’re basically rebounding in your connective tissue, there is not much eccentric muscle action going on at all, that is most likely suboptimal for muscle hypertrophy.

Moreover, it’s probably really hard on the joints because when the muscle is not decelerating the weight, it will be the connective tissues that are doing it. In that sense, theoretically, you would also expect that slower eccentrics are better for the stimulus to fatigue ratio in terms of how much stimulus you get for the muscle tissue versus how much strain there is on the connective tissues, like the tendons. This remains somewhat speculative, but in physiotherapy circles the benefits of eccentric training are well recognized. For strength development too, there was no effect of eccentric repetition duration on how much strength people built. I would note that in volume equated studies, there was a trend for better strength development with slower eccentrics. If anything, you would expect the opposite. But that’s because in this case, we have two groups that are doing the exact same exercise, but one of them is doing it with slow eccentric and the volume is the same, then that group is simply training harder. If I have to do certain weight for a certain number of repetitions, and I have to do it more slowly, of course it gets more difficult, so you’re just training harder. In non volume equated studies, which is how it normally is, if you do very slow reps then you cannot do as many of them, there was no effect on strength development.

Study #2 compared dumbbell biceps curls to supinated grip dumbbell rows. Which do you think was more effective for the biceps? If you think the rows for the more effective biceps builder I pitty you fool. Of course rows were inferior to curls for the biceps. However how inferior exactly where they? In this study, the rows only built 38% of the biceps mass as curls. This is in line with prior research, which found that rows grow to biceps approximately half as well as dumbbell curls. So for program design purposes you should count exercises like dumbbell rows only half towards your biceps volume.

The 3rd study found that strength gains and size gains are very strongly correlated, even in untrained individuals, when study quality is methodologically very sound. In many studies, strength gains and size gains don’t correlate very well. This has led many people to conclude that the size gains in high volume studies, for example, are just edema, just water retention, not contractile tissue, otherwise, we would have also seen correlation with strength development. I covered that issue in that video. Short version: It’s probably not just edema. The researchers of this new study also concluded that strength and size are in fact highly correlated, and the reason we don’t see this in all studies is simply a matter of study quality.

The researchers of the current study improved on prior studies in multiple ways. For one, most studies are only 8 weeks long. This study was 15 weeks long. Most studies are 8 weeks long because most studies are conducted at a university, and that’s the length of a typical college semester. So in longer studies we actually much more reliably see that strength and size gains start correlating. People that get more muscular also get stronger. In In a short study it’s easy to miss this because most of the strength gains in the short term are neural in nature. It’s just getting better coordination. The effect of muscle mass is not very pronounced because you don’t build that much muscle in 8 weeks.

The researchers also used MRI scans which are the gold standard compared to things like ultrasound or DEXA scans, which are not as reliable. Furthermore, the researchers did every measurement of both muscle size and strength twice. This reduces measurement error. And last but not least, the researchers had a decent sample size of 39 individuals, and much more importantly, the measurements of strength and size were conducted in the same individual. That is, of course, what we care about, but many studies look at strength and size and compare them across different individuals or across different studies. That is very different, and then of course, the relationship weakens dramatically because you’re not just comparing differences in strength and size gains, but you’re looking at different individuals with different diets, different lifestyle, different genetics, etc..

The practical implication of this is that your strength gains on familiar exercises that you’re doing long term in your program are a very good measure of muscle hypertrophy. Arguably, strength gains are one of the best measures we have of muscle hypertrophy because measuring muscle hypertrophy is very difficult. Looking in the mirror or doing your circumference measurements is really not going to cut it. So most people when they say “This worked for me, bro!” really have no idea if it worked for them because they have no good measure of muscle hypertrophy. In contrast, when you put 50 pounds on your all time PR for the squat, it’s very likely that your quads will be bigger.

Next!

Study #4 looked at whether you should wear a belt during squats. Many people simplistically reason that if you wear a belt you can lift more weights and therefore you should gain more muscle. That is probably not the case. The study found no effect of wearing a belt on electromyography muscle activity readings. Now, EMG research has its pitfalls, but this finding is in line with multiple prior studies as well as studies on ground reaction forces. Both in a squat and in the deadlift wearing a belt does not seem to increase ground reaction forces. This means that you’re not putting more force into the ground, your muscles do not seem to be more active, but you are lifting more weight around 10% on average if you’re using the belt well. How can this be?

Well, it’s mostly a matter of increased stability and intra abdominal pressure. If you think of slamming a hockey stick into a ball, and a hockey stick is made of a flimsy rubber, you’re not going to put a lot of force into the ball because you lose a lot of the force in the hockey stick. If the hockey stick, however, is made of metal, most of the force that you put into the hockey stick also goes into the ball. It’s kind of like that with squats and deadlifts where if you don’t have a strong core or if you’re not wearing a belt, your core will always be a little bit more flimsy than if you do wear a belt, then there is less force transfer, if you will, compared to when the core is fully rigid. I will say that the new study was not great because it used submaximal weights, but based on the overall literature I think you’re not really missing out if you’re not wearing a belt for your squats and deadlifts. If you do like wearing a belt, it’s great, it’s fine, but I wouldn’t expect more muscle hypertrophy or strength gains from it. You’re just lifting a higher total weight to get similar muscle activity. That’s generally only really beneficial if you’re a strength athlete that can also where the belt in competition. Then you should prepare for that by also wearing a belt in training. For other lifters, it’s mostly a matter of personal preference.

You still there? Good.

Study #5 looked at lengthened partials versus full range of motion training. Lengthened partials are the new kid on the block that is challenging the king of full range of motion training. Lengthened partials mean that you’re doing partial range of motion repetitions usually only doing the bottom part of the movement when the muscle is in a lengthened position. The idea with lengthened partials is that muscles generally seem to grow more when they are trained at longer muscle lengths, possibly due to a combination of higher active and passive mechanical tension, and therefore it makes the most sense to only train at that length of the muscle. In this specific study, a group of trained lifters trained one of their arms with preacher curls doing lengthened partials, only doing the first part of the movement, and the other group did full range of motion repetitions.

Now I will say from the bat here that I think the choice of preacher curls is not a great one, because preacher curls inherently overload the biceps in the bottom position. So you’re not going to find a very big difference in the stimulus between full range of motion and lengthened partials. Indeed, after eight weeks, there were no major differences in muscle hypertrophy or strength gains between the two groups. Now, there was weak to moderate evidence for somewhat greater gains in the lengthened partial group, which is interesting given that the preacher curls already overload the bottom position. But statistically this evidence was again weak to moderate in strength and strength gains were actually slightly better with the full range of motion.

However, I think that was because strength was measured with a full range motion, so it makes sense that full range of motion training is best for a full range of motion 1RM strength. At which range of motion strength was measured was not entirely clear to me. This is still a preprint. It has not been accepted for publication yet, so that’s something to note. Overall, I would say that lengthened partials have not lived up to the hype that they have received on YouTube over the last 2 years. However, on the other hand, you could also argue that the lengthened partials are at least as effective or full range of motion training and possibly more effective. I think lengthen partials make a lot of sense for exercises that don’t inherently overload the muscle in a lengthened position. Think of most leg extension machines and calf raises, for example. For other exercises I would not expect much, if any difference between lengthened partials and training with a full range of motion. Practically speaking, I think full range of motion training is easier for a lot of people. It’s a little bit easier to push yourself, and it’s easier to measure progressive overload because you have a clear point A to point B from which you count all your repetitions. And in my experience, most people also prefer training with a full range motion, so I use length with partials mostly in the later sets of exercises that don’t overload the muscle well at long muscle lengths without lengthened partials.

Last but not least, study #6 provided a compelling debunking of the idea that isometric training, in which the muscle does not change length, and usually you’re just in a static position, is inherently inferior to full range of motion training. Researchers found that this is probably not the case as long as you do the isometrics at long muscle lengths. The researchers had a group of trained individuals train their legs with leg extensions. With one leg they did full range of motion repetitions to absolute failure. With the other leg for a similar duration of time, which was about 30s per set. They just pushed as hard as they could in the absolute bottom position of the rep, doing an isometric contraction, a static contraction in which you’re not actually moving, but you are trying to produce as much force as possible. In this study, the leg extension machine, and this is an important part, had more range of motion than most machines. The leg was essentially fully bent.

Most leg extension machines do not allow your leg to go back as far. After six weeks quadriceps muscle growth was similar between the legs. It was actually 1.9% in the leg doing isometrics versus 0.8% in the leg doing full range of motion training. However, this difference was statistically unclear due to the minor effect sizes of having trained individuals only trained for 6 weeks. Nevertheless, this study provides compelling evidence that isometrics are at least not worse and possibly even superior to full range of motion training if you compare an exercise which does not overload the muscle well at long muscle lengths, and you compare that to an isometric contraction, which specifically does the contraction at very long muscle lengths. Prior research has suggested that isometric contractions are inferior to full range of motion training, or at best, equally effective. In the studies where muscle growth was worse, we’re generally looking at relatively short muscle length isometric contractions. Thus, the effectiveness of an isometric muscle contraction seems to depend crucially on at which length you perform it. Isometric muscle contractions are probably not inherently inferior to training with a full range of motion.

During isometric contraction force production and mechanical tension in the muscle can actually be higher than during a concentric muscle action. Lower than during an eccentric muscle action, but you’re not really overloading the eccentric anyway during traditional training, because your load is limited by how much you can lift concentrically. Isometric exercises do miss out on a stretch reflex and a stretch shortening cycle, so this could be a factor, but based on the totality of evidence so far, it seems that isometric muscle contractions are not inherently inferior to training with a full range motion. This is practically important for exercises like planks, deadlifts, and squats, especially for core training, because these exercises are probably actually very effective. And this could explain why many people don’t need to do a lot of lower back training when they do a lot of squats and deadlifts. The erector spinae are only trained asymmetrically during squats and deadlifts, but they actually grow pretty well in many train lifters. Moreover, in a previous video, I speculated that deadlifts are actually surprisingly effective for the traps, in part because it’s an isometric long length muscle action. This evidence supports that.

There! You are up to date again on the latest science of muscle hypertrophy. If you like this type of evidence based content, I’d be honored if you like and subscribe. And if you want to go into a deep dive of how to build muscle in the most optimal manner possible, check out my online PT course. You’ll learn absolutely everything there is to know about how to take your physique to the next level, as well as develop strength, health, and how to stick to your diet. Check it out!