Dr. Patrick: I mean, for the longest time, you know, I remember hearing, "Lift heavy," or, "lift big or go home," or something like that. I mean, you're like, you know...

Dr. Schoenfeld: "Go heavy or go home."

Dr. Patrick: Yeah, that's it. Like, what does the science say about that? Like, you know, you've really contributed to this area about, "Do you need to train heavy to get your gains?"

Dr. Schoenfeld: So, this is an area that I've done pretty much one...so, I've changed my opinion on so many things, you know, that I had learned as an up-and-coming sports scientist and that were treated as dogma, you know, in textbooks, my views have, in certain respects, done 180 and nothing can be characterized more so than loading. So, I had always thought that, if you're doing anything over 12 to 15 repetitions, it's basically glorified cardio and that, you know, it's just muscle endurance, you're not going to gain muscle. The literature has now compellingly shown, there's so much literature on the topic, our lab has done quite a bit of research, as well as many others, and it shows that you can gain muscle, similar amounts of muscle regardless of the loading across a wide range of loading spectrums, up to 30 to even 40 repetitions, which is a long...that's a long set. And that's at the whole muscle level.

Now, there may be, I want to really emphasize, this is still equivocal, there may be some muscle-fiber type-specific benefits to doing light loads for type-1 fibers and type-2 fibers for heavy loads. If you're asking my confidence in that literature, it's, you know, modest at best but I can't rule out that that would be the case. But when you're looking, let's say, at MRI data or ultrasound, which we've used extensively, it really shows no difference. And I'll tell you what I think is a quite funny story, looking back, but Stu Phillips had published a study, circa 2012, and he went on social media, it was Facebook at the time, and it was on untrained subjects doing leg extensions. And it showed that there was no difference in the whole muscle hypertrophy between 30% 1RM, which is like 30 reps, versus 80% 1RM, which was like 8 reps. And I remember it as clear as day saying, "Stu, come on, this is untrained subjects doing leg extensions,they get jacked from doing spin cycling," that was I think my exact quote. And I said, "I'm going to do this study in trained individuals, you're going to see there's going to be no question the older individuals are going to need the heavier loads to get those highest threshold motor units, the type-2 fibers, into play."

And lo and behold, I carried out that study, no difference. It was really [inaudible 00:47:14]. And since then there's just been so much evidence, not only just across the spectrum of populations, untrained, trained, older, younger, men, women, really any and every population has been extensively studied. And it really is a beautiful thing because it provides so much flexibility and options to carry out resistance training. And it's particularly I think beneficial for issues like training through injuries. So, if you're training through injuries, you know, heavy loading can be contraindicated. And also particularly for the older individuals because joint-related issues, as you know, as people get older, they get osteoarthritis and other joint-related issues where heavy loading can be very uncomfortable for them and perhaps debilitating. So, it's kind of contraindicated. And they can use lighter loads.

Now, the caveat to this is is that the lighter loads have to be taken with a high degree of effort. So they have to really...if you do not extensively challenge your muscles, meaning that the last few reps are difficult to complete, you're not going to achieve gains. So, when I talk about light loads, it's not this, you know, taking pink dumbbells and just, you know, doing some lifting, "Okay, I stop," you must challenge the muscle. So, when you lift heavier, just innately you're going to challenge the muscles regardless because the weight is already heavy. With lighter loads, the first number of repetitions are very easy to complete and, if it's easy to complete, you're really not doing much for challenging.

And this goes back to a survival mechanism. So, I think this is important, because the reason that the body adapts to strength training is survival. The reason that the body adapts to anything is through a survival mechanism. And if you are not challenging it in a way it is not accustomed to being challenged, it has no impetus to adapt. So, the reason that you will get these adaptations in strength, and power, and hypertrophy, muscle endurance, bone density, etc., is because the muscles and bones, etc., tendons, ligaments are being challenged beyond their present capacity.

Dr. Patrick: And so, as you get stronger, then you have to push past that and challenge them more. So, the big take home for lifting lighter, which is what I tend to do, is to get fatigued, right?

Dr. Schoenfeld: That's correct.

Dr. Patrick: ...when you're doing it, and so, it often means more reps. Which I enjoy doing. I've done both and I do find, for me, I like doing the lighter lifting and more reps versus doing heavier and fewer reps. And I also notice I'm less likely to injure my wrists if I'm doing...now, if I was doing things like proper form and all that, maybe it wouldn't be such an issue.

But you mentioned the muscle type 1 and type 2 fibers, and maybe there's some evidence that lifting a little heavier might help shift a little bit more type 2. Can you talk just for a moment, like, what are the roles of those types of fibers and should people aim to kind of gain both of those? Or are there distinct differences, you know, in terms of with aging, their roles in aging?

Dr. Schoenfeld: Yeah, yeah. So, great questions. So, I'll tackle the second question first. Yes, aging is mostly specific...so, when I say "aging," what's called sarcopenia, which is the age-related loss of muscle is most specific to the type-2 fibers, which are your strength-related fibers. So, just to kind of even circle back for those who don't know, type-1 fibers are endurance-oriented fibers, they do not produce force as well as type-2 fibers but they're indefatigable, they can go on for longer periods of time, they're hard to fatigue. Whereas your type-2 fibers fatigue relatively easily but they have the capacity to produce greater force.

As you age, the type-1 fibers are more well preserved, whereas the type-2 fibers, there's even what's called apoptosis, which has been shown as a loss of fibers. But certainly there's a diminishment where the fibers get smaller and smaller. It's more specific, the sarcopenic effect is more specific to the type-2 fibers. Which is, obviously, problematic because the ability to produce force is where your primary functional capacity, at least from being able to open cans and, you know, jars, avoiding falls, etc. Circling back, so, then the training effect, I want to emphasize, if you are training hard regardless of heavy/light, you're going to be targeting both 1 and 2-fibers. So, we're talking now nuance. So, I think this is where this kind of gets lost in context that where I think this would have the, if it is in fact true, greatest relevance would be to, let's say, bodybuilders who want to maximize their muscle development, it probably is beneficial to utilize some heavier training and some lighter training so that you at least make sure you're kind of hedging your bets and make sure that you're maximizing development of all fibers.

For the average individual, if you are training hard, regardless of light or heavy, you're going to be getting type-1 and type-2 fiber development. And it's been well documented that light load training does target the type-2 fibers. Which was one of the myths, it used to be taught when I was an up-and-coming sports scientist, that, if you just use light loads, you would not activate the highest threshold motor units, which are associated with these type-2 fibers, and thus you would not optimize your strength and power and hypertrophy.