Lifting Weights Builds Flexibility Better Than Stretching (New Research) | Ep 459
Do you need yoga, stretching, or "mobility work" to stay flexible. Does lifting weights make you "stiff" or does it improve flexibility?
We examine 3 recent studies that compared resistance training to stretching for flexibility, and their findings challenge everything most people assume about lifting weights and mobility.
Philip covers the "lifting makes you stiff" myth and a training approach that builds flexibility and strength at the same time.
If you're over 40 and worried about losing range of motion, this one's for you. Stay for the bonus 60-second squat test at the end.
Upgrade your sleep to match your training with Cozy Earth. Cozy Earth's bamboo-derived sheets regulate temperature so you stay comfortable all night. 100-night sleep trial, 10-year warranty. Use code WITSANDWEIGHTS at witsandweights.com/cozyearth for up to 20% off.
Timestamps
0:00 - Lifting weights and flexibility
1:10 - Strength training and mobility after 40
3:00 - Partial range of motion and stiffness
6:12 - 3 recent studies on strength training vs. stretching
8:30 - Bodyweight exercises and flexibility
10:22 - Eccentric training and range of motion
12:38 - 2025 Delphi consensus on stretching
13:31 - The best way to improve recovery
14:49 - Full ROM on compound lifts
16:30 - Exercises that load muscles at long lengths
18:00 - Load intensity and flexibility gains
19:30 - Exercise substitutions for flexibility
21:00 - Olympic weightlifters and mobility
22:34 - Bonus: 60-second squat flexibility test\
-
Philip Pape: 00:00
If you've ever spent 15 minutes foam rolling and stretching before a workout because you think lifting weights makes you tight, I have some news. Three separate meta-analyses, the most recent from 2025, all found the same thing. Full range of motion strength training produces the same flexibility gains as dedicated stretching. And one type of training, the eccentric or the lowering phase, actually produced bigger improvements than stretching alone. Today I'm covering exactly why the lifting makes you stiff myth exists, what the research says about how your muscles get more flexible under load, and the specific exercises and training approach that build strength and flexibility at the same time. Plus, stick around to the end because I'm going to walk you through a 60-second squat test that tells you exactly where your flexibility stands and how to start building full-depth squats from wherever you are right now. Welcome to Wits and Weights, the show that puts a popular piece of fitness advice under the microscope, finds the hidden reason it doesn't work, and gives you the deceptively simple fix that does. I'm your host, Philip Pape, and this episode is for anyone who's ever avoided lifting weights because they're worried about getting stiff or having more flexibility first, or who spends a chunk of their training time on dedicated mobility work because they assume their strength training maybe is working against their flexibility, or they can't even do it until they're flexible enough. All of those things apply. Maybe you're a little bit on the older side. By older, I mean over 40, and that's me. And you've noticed that your range of motion isn't what it used to be. And someone said, hey, you got to do yoga or you've got to do Pilates or some elaborate stretching machine. And, you know, no judgment. Those things are fine. I have nothing against them. Maybe some things against them, depending on the claim. But the research on this topic has actually gotten more clear in the last few years. And it tells a really good story that I've been talking about for a while, but it's nice to have the evidence to back it up. So you're gonna learn three things today. First, why the belief that lifting weights makes you stiff is based on a specific training mistake, not on what lifting does to your muscles. Second, what three separate meta-analysis have found when they compared strength training to stretching for flexibility, and why the numbers they found are actually quite convincing. And third, the specific way to program your lifts so your training sessions build flexibility and strength simultaneously, and you don't have to do any extra stretching. Now, isn't that nice? And remember, at the very end, I'm sharing that 60-second squat test I mentioned in the teaser. A simple weight that you can figure out where your flexibility is right now and how to progress to build it, even if you can barely get to parallel right now. All right, let's get into it and talk about this myth, which you may or may not hold, but it's gonna lead to the other topics we're covering today.
Philip Pape: 03:00
And it goes like this lifting weights makes you tight and bulky. If you want to stay flexible, you need insert method here yoga, stretching, dedicated mobility work. Or in some cases, you know, you can't even lift weights until you get flexible enough. And this is one of those beliefs that it feels like it has a lot of truth because, you know, you see these, if you see ever seen a very muscled bodybuilder who can like who has trouble scratching their own back, you know, somebody who's jacked in the gym, can bench multiple plates, but can't touch your toes or get into a deep squat or whatever, which I don't even, I don't even think that archetype exists as much as we say it does. But if it did, you know, the conclusion is, oh, lifting did this to him, right? Lifting made him stiff. The solution has to be something other than lifting. Because if you lift weights, if you're just a bodybuilder, if you just do single plane of motion lifting, if you just focus on strength or powerlifting, whatever, you're not gonna have the flexibility. But that concluding that is a leap of logic. It is skipping the question, hey, how was that person lifting? Because here's what I have noticed in that the people that look or act like that, they might have they might have some muscles like show muscles, but they might also they're probably training partial ranges of motion, like quarter squats, like half half-rep benches, you know, curls where they're just cheating and the elbow never extends, or leg presses that never break, you know, past 90 degrees, and and loading muscles to the shortened positions and never working under tension or under long lengths, you know, under full range of motion. And this actually matters because the stimulus that improves flexibility, the thing that actually makes a muscle a little bit longer, more extensible over time is tension at long muscle lengths. Now, I'm not saying just go out and do long length partials. There's plenty of research that backs up that you, you know, having full range of motion, so you cover the short and long length is probably the best move here. But the stretched position, the bottom of a squat, the bottom of a Romanian deadlift where your hamstrings are loaded at their longest, or the overhead position of like a tricep extension, when you train through a full range of motion, you are stretching the muscle under load on every single rep. And that's really important. So people who, for example, get stiff from lifting are probably getting stiff from not going through the full range of motion and avoiding the positions that would maintain or improve their flexibility. And the whole stiff thing, that's just one stand-in for any number of lack of flexibility issues that you might see in someone who otherwise maybe looks a little bit healthier fit. So if you like analogies, I want you to think of it this way: if you get like a door hinge and it never opens past 45 degrees, it just kind of opens part way, partway, partway, partway. It often will get stuck or it'll rust in place and it'll never get past that point. Not because the hinge itself is broken, but because it hasn't been using used through its full range. I don't know if that analogy is helpful. It's what came to mind, but your joints kind of work like that. If you use the range, you keep it. If you don't use the range, you lose it. It's an adaptation. It's an adaptation. So I don't want to just make this me going off on a diatribe.
Philip Pape: 06:12
I want to look at the research. Okay. So I mentioned three separate meta-analyses that have compared resistance training to stretching specifically for flexibility outcomes. And I want to walk through each one just real quickly because I think they build on each other and together paint a really clear picture of what we're talking about. The first is Afonso and colleagues. This is 2021. This is 11 randomized controlled trials with 452 participants comparing strength training to stretching for range of motion improvements. And the result was there was no difference, no statistically significant difference. The effect size was negative, 0.22, which slightly favored stretching, but it wasn't significant. The p-value was 0.206. And there was a subgroup analysis that showed no differences whether they measured active or passive range of motion, whether they looked at hip flexion or knee extension, whether the studies were high or low risk of bias. They all came back the same. Basically, the two were equivalent for flexibility. Now that was a small study, again, 11 studies, 452 people. So we have a bigger study published in sports medicine in 2023 by Aliziday and colleagues. And this is a larger one. 55 studies, over 2,700 participants, and they asked three questions for the study. First, does resistance training improve range of motion compared to doing nothing? Yes, no surprise. There was actually a pretty highly significant moderate effect size, 0.73. Second, does resistance training match stretching? Essentially, yes. The effect size of 0.08 compared the two, p-value of 0.79, no meaningful difference. So in other words, they were about the same stretching and resistance training. Third, does adding stretching on top of resistance training improve flexibility further? No. Effect size was negative 0.001. So if you're already training through full range of motion, adding a stretching program on top of that gives you exactly or approximately zero additional flexibility benefit. There was a very big effect size, it was 1.042. Trained individuals or active individuals still improved a little bit, but it was smaller, around 0.43. So if you've been sedentary, if you start lifting through full ranges of motion, you're gonna have huge gains in flexibility. And if you already train, you're gonna have some moderate gains in flexibility. They also found that bodyweight exercises did not significantly improve range of motion. Only exercises with external load, free weights, machines, resistance bands produced significant improvements, which tells us that yes, load does matter. You need actual resistance pushing you into those end range positions. So that's the second study. The third one, the most recent meta-analysis, was by Favreau and colleagues. It was in the Journal of Strength and Conditioning Research just last year, 2025. 36 studies, nearly 1,500 participants, and they confirmed the overall finding we've been talking about that resistance training significantly improves flexibility, and they had a medium to large effect size of 0.63 compared to the control group. But they also found something new, and that is related to intensity. That intensity is important. High intensity resistance training produced a significant effect size of 0.75. Low intensity training was only 0.28 and not statistically significant. So that tells us it's not just about going through the range of motion. You also need meaningful load through that range of motion. And by the way, when we talk about intensity, we're talking about load. We're not talking about like sweating or endurance or something like that. All right, now let's
Philip Pape: 10:22
get a little bit more specific because there is a separate body of research on eccentric training. That is the lowering phase of a lift. And when you look at that compared to flexibility, okay, so there's a study by Kay and colleagues, or not a study, but a meta-analysis. I love meta-analysis because they take, they take many, many studies and look at them to give even higher quality findings. And this was in medicine and science and sports and exercise from 2023, and it was 17 studies, 376 participants. They looked at eccentric resistance training and lower limb range of motion, lower limb meaning your legs. The overall effect size was large at 0.86, 86. For ankle dorsiflexion specifically, the effect size was really large, 1.12. Okay, and again, that's compared to that's showing that they improve flexibility. Then there was a systematic review by Vetter and colleagues in 2022 that also found a centric eccentric training improved range of motion by 9% on average. But concentric only training, which is just the lifting phase without controlling the lowering phase, produced no measurable change in range of motion. So the eccentric phase, which is the controlled lowering, where the muscle is lengthened under tension, is the primary driver of the flexibility improvements from resistance training. Right. And this actually makes mechanical sense if you just put a put on your engineering hat. When you lower a weight through a full range of motion, what are you doing? You are stretching that muscle while applying that force, that load. Right. And that is the same stimulus that a static stretch would provide, except you're also getting the strength and hypertrophy benefits under load at the same time. Pretty cool, right? Now the research community issued a consensus statement. This is 2025 Delphi consensus statement. It's from 20 leading stretching researchers across 12 countries. And they said, hey, full range of motion resistance training produces flexibility gains, quote, at least a similar degree, end quote, to stretching, especially when the eccentric phase is emphasized. And they concluded
Philip Pape: 12:38
that, okay, if you're a healthy adult, the choice of method for improving range of motion, quote, can be left to individual preference. So that's pretty cool to see a verbalized scientific consensus that resistance training improves flexibility. So I walked you through the research on how eccentric loading, that controlled lowering phase, drives flexibility adaptations. And then those adaptations, like the fascicle lengthening, the tissue remodeling, to get nerdy about it. It all happens when? That those adaptations happen when? Come on, during recovery, right? During recovery, specifically during sleep. Your muscles are not going to rebuild while you're in the gym. They're going to rebuild when you're resting, which means the quality of your sleep directly affects how well your body responds to training. So here we have another natural, totally unscripted, just kidding, segue
Philip Pape: 13:31
into our sponsor for today, Cozy Earth. I tried, and now I'm owner of at least two sets, not at least two sets, exactly two sets of Cozy Earth's bamboo-derived sheets. And they're awesome. They're made from viscos derived from bamboo. And what they do best is regulate temperature, other than feeling silky, smooth, and really comfortable. They help you if you run hot at night or if your partner's freezing and the other's overheating. The sheets actually solve it in both directions because they wick heat and moisture away from your body. And then you stay comfortable throughout the night. So if we're talking about sleep quality, something that's on you your entire night is a massive variable in the equation. So that's why I'm a big fan of them. And if you spend 2,500 hours a year in bed, you're already investing in your training and nutrition, those eight hours deserve a lot of attention. So I love these. Go to witsandweights.com slash cozy earth to get 20% off with the code Wits and Weights. They have a hundred night sleep trial and a 10-year warranty. So you can basically test them for three months. And if you don't love them, you send them back and they'll give you a refund. Go to wits and weights.com slash cozy earth. And you know, if you take their survey, let them know you heard about it on Wits and Weights. But at the very least, go check it out. Witsandweights.com slash cozy earth. All right, so let's get into the fix for how to improve flexibility.
Philip Pape: 14:49
All right, if you understand the mechanism, you don't have to have a separate flexibility or stretching program. All you have to do is train through full range of motion with meaningful load, emphasize the eccentric phase of your lifts. And some of you are thinking, wait a minute, the eccentric phase, now we're getting into that funky stuff. Does that mean we have to use negatives? Is that no, you're gonna find out that what we're doing here is not different than what I've recommended in the past to begin with, which is great. Great. You don't have to learn anything new, okay? Let me give you the specific principles and then the exercises. So principle one is full range of motion on compound lifts. If you haven't been doing this, do this. If you're an advanced lifter, there's definitely places where you wouldn't use full range of motion. But this is the principle for getting into the full range, both the eccentric and concentric, and also the lengthened and shortened positions. So this means getting your squat below parallel, not a quarter squat, not too parallel, below parallel means the hip crease below the patella, means your butt below your knee. It means if you're doing a Romanian deadlift, you need to have a genuine stretch of your hamstrings at the bottom, which if you're, again, flexible already, could be taking the bar all the way to the ground, or if you're uber flexible, could be standing up on a block or pads so that you can go even further. It means with your overhead press, they're gonna start from your shoulders, not your chin, right? You're gonna come down. It means rows and pull-ups that reach full arm extension at the bottom, right? Not just coming part way. If you are cutting range short on these movements, then you're just leaving the flexibility on the table. So if you complain about flexibility to me and say, like, I need flexibility because I need a lift, I'm gonna say, are your lifts already in full range of motion? Or you know, yeah, the full range. Principle number two is to include exercises that load your muscles at their longest position. So this is where selection gets a little bit strategic. So for biceps, an incline curl, for example, is fantastic because you're at an incline. So when you open up your arm down to the bottom lower position, you're gonna go even wider in terms of a length, a longer length. So for triceps, an equivalent would be an overhead extension, is one of my favorite moves. If you had to do one thing, I would do an overhead extension. That could be with cable, with an easy curl bar, uh, with dumbbell, it doesn't matter, just do it overhead. Um, hamstrings, we've got the Romanian deadlift or a stiff leg death deadlift, you know, from a deficit that'll put your legs under a much greater stretch than, say, a leg curl. Calves, I mean, even the body, even the show muscles and the bodybuilding stuff, standing calf raises from a step where your heel drops way below platform level, where you could stretch at the bottom and load the what they call the gastrosinemius at the long position, any of these exercises will double as both strength and a loaded stretch. And for much of what you're doing, there's an opportunity to do this anyway. But sometimes you have to pick exercises that really maximize it. Principle number three is to control the eccentric. Now, this is the one where I'm going to, I'm not gonna get weird. Okay. So remember we talked about eccentric training that that helps with the improve, it improves your range of motion, having the eccentric in there. Now, by definition, you're gonna have the eccentric in there, but what you don't want to do is just drop the weight or bounce out of the bottom position. And this is important because you know, when I learned the low bar back squat, I learned to use a stretch reflex at the bottom, which is super helpful. And there are benefits to that for sure. And you don't have to pause. I will say, however, adding in a pause could be beneficial, especially if you're trying to get this extra flexibility stimulus, but even just doing it in a controlled fashion. So if you're gonna squat down, you squat down and you bounce out of the bottom, but it's not like a big shock bounce. It's not like a CrossFit thing. You know, it's not like you're banging out the reps. It's still very controlled. And I would say on the way down, you know, a two-second, up to three second lowering phase is fine. You don't have to actually extend it further. We're not talking about time under tension. We're simply talking about the flexibility piece of loading into the full range of motion. So just doing it under control is really important. And then, of course, as always, explode into the concentric. That's a different topic, but it's an important thing to do. Principle number four is you gotta train with real load. You've gotta train with real load, right? Doing stuff at body weight or high reps and never going up in weight, never having load, especially if you're doing partial ranges to begin with, right? But even if you're doing it full range of motion, you're gonna quickly tap out on the benefits until you increase with load. Well, guess what? If you're applying progressive overload, you're gonna do that anyway. You're gonna have to increase the load anyway, right? We're not talking about maxing out and grinding. I'm talking about getting close to failure like you normally would for mechanical tension. Well, the same principle applies here. So you see how it all naturally works together if you're lifting the right weight anyway. So I want to give you a couple substitutions that might help with flexibility while you're building strength. So let's say you're doing leg presses and for whatever reason you're getting limited depth, you could swap in goblet squats or front squats, where they often make it easier to go super deep and then progressively work deeper and then translate that over to something like a leg press. All right. And I I only say this because I know some people have different hip limitations when they start doing some of these exercises. So it's it's a matter of not having an excuse, but rather building that range of motion in an as natural way as possible. It might be bench, it might be belt squats, might be hack squats, but you get my idea. If you're doing something like leg curls, like these isolation movements, I would go to a compound lift like a Romanian deadlift. RDLs are great for hamstrings, let me tell you. They're so good. Also, good mornings. Good mornings can be a little tricky though on the upper body if you're not used to them. So Romanian deadlifts can be loaded super heavy without, you know, with a pretty good form for most people. If you're doing, say, press downs for your triceps, right? Very popular, fun thing to do is take cable press downs and add in or replace them with overhead dumbbell extensions or overhead cable or easy bar extensions. And then if you're doing regular barbell curls, which I do love barbell curls, and I would say when you get to the bottom, stretch them out and wait a second and come back up. Don't just bounce out of the bottom. But inclined dumbbell curls, let me tell you, are awesome. Kind of related to that would be preacher curls or spider curls, either two-handed or even one-handed on the back of an inclined bench where you can really get that angle of the stretch, that long, like that length of position. And then I mentioned the calf phrases before where you really should be up on a step so you can get a stretch at the bottom. It's not the concentric where you're pushing up that's as important as the bottom stretch. So you don't have to overhaul your entire program, just do a couple swaps. I'm I'm a big fan of swaps no matter what. Even when I follow a program that's somebody else's or my coach's, unless it's fully custom, I'm always going to be making swaps anyway, just for different things. I'll add a slingshot over here, a block over here. Thanks, Tony. Shout out to you. I'll do a, you know, I'll do a what am I trying to say here? A different angle, a different variation, a machine versus a dumbbell, whatever. You know, and and just one quick side tangent. If you think about Olympic weightlifting, the snatch. The clean in jerk, these guys are really strong, but they're also really flexible. And they didn't do it through stretching, they did it through the lifts themselves, right? And they're they're putting themselves under load, full range of motion, all the time. There was actually a study in 2022 of master's weightlifters. So this is age 35 to 76, that found that their shoulder range of motion exceeded the general population and functional capacity was greater than age match people who don't lift, but only 5 to 20% of them supplemented with something like yogurt Pilates. So meaning you lift weights, you get
Philip Pape: 22:34
more flexible. All right, as promised, here is a quick test to find out if your squat depth is limited by flexibility, by your motor control, or by something else. I want you to find a box or a bench or a sturdy chair that is about knee height. So not like a tall, what do you call it, stool or something like that, but a short, firm surface about knee height. I want you to stand in front of it with your feet roughly shoulder width apart, knees pointed slightly out. Now sit down to the box slowly, take about three seconds to lower yourself all the way to the box, and then stand back up. If you can do that with your heels flat and your chest up, then your flexibility is not the problem. You have the range of motion. You have it. You just have to start loading it. Okay. And this is problem one that with most people, if I say, can you sit down to a box and get back up? And you can, you're good. You have the range. Now, if your heels pop up or your chest collapses forward or something like that, maybe you have a little bit of an issue with your ankles or hips. You can, you can what you can do is put a rolled towel or a plate, you know, a small like five-pound or 10-pound plate under your heels and try it again. And if you're able to do it, then okay, maybe there's something with your ankles we have to look at, which again is typically resolved just through the squatting itself. But a lot of people have just, you know, poor ankles for a variety of reasons. And and one way to strengthen them is work on calf raises from a deficit or do goblet squats with your heels elevated until you build a range to go flat. You know, I when I started squatting, I was able to squat in, I'll call them normal flat shoes and you know, weightlifter shoes with a heel, but it was a little bit tough for me to do it barefoot, which was an indicator that, you know, I had a little bit of a lack of flexibility, but it very quickly resolved itself just by squatting. Now, once you can sit to the box comfortably, guess what you do? Lower the box height. So this is where if you have a stack of plates or something like that, or if you're lucky enough to you have a plyometric box that's just really low, like 12 inches, but some way to drop it, heck, even if it's big, thick books that you've got to stack up. And you're gonna drop it. And the idea is you want to eventually be able to sit to a low box at about 12 inches, 12 to 14 inches, where you're doing it under control, your feet are flat. That demonstrates you do have the range of motion for a proper deep squat. Again, a lot of you can just already do this. And from there, you have to load it. So you can load it in front with like a dumbbell or kettlebell at your at your chest, like goblet style, and then start building strength of that range. Or you can load it on the back with a dowel or a light barbell or a full-on barbell again, depending on how strong you are, just loading it. I mean, I would prefer the barbell if you're gonna eventually do the barbell squats, but you can do it in really any way you want. So you're gonna control the eccentric, you know, two, three seconds at most, lightly sit on the box, but don't let go of all of your tension. Hold on to that tension and then squat back up with explosiveness. And that's how you get started. Okay, and you're gonna build your strength and flexibility.
Philip Pape: 25:36
You're gonna be just fine. You don't have to do anything extra. All right, anyway, if you know someone who is having trouble with their flexibility, send them this episode, let them listen to it. Maybe it will open their eyes and ears to all the new possibilities. Until next time, keep using using your wits, lifting those weights. And remember, lifting is the best stretching tool you already have. You just gotta do it. I'm Philip Pate, and I'll talk to you next time here on the Wits and Weights podcast.
