 So in today's society, stiffness is viewed as a bad thing, right? You're stiff, that's essentially synonymous with your unfit and lazy. You're stiff or old maybe. Being flexible on the other hand is viewed as like, oh amazing, amazing. If you're flexible, you're healthy. Oh, he's so flexible, he's so flexible. Oh, she's really stiff. You know, and you see people at the gym and they're super flexible, they're doing their stretching and you think to yourself, at least I sometimes use to do this, I look at them and I'm thinking like, wow, I wish I was that flexible, I can't even touch my toes. Here's the thing though, if you're a runner, the question you should be asking yourself isn't, am I flexible enough? It's actually, am I stiff enough? Let's get into it. So I'm sure most of you have heard what cyclists talk about when they talk about their bikes, right? They say, oh, it's such a great bike, it's super stiff, right? I'm sure some of you heard that. Cyclists talk about the stiffness of their bike. That's one of the reasons why carbon forks and a carbon bike is so great because it's so freaking stiff. Why is that good? Why do cyclists like a stiff bike? If you've ever used a suspended bike, you know, I don't know what it's called, full suspension bicycle, you know, the ones they use for off-road, mountain biking, downhill biking typically with like suspension in the middle and on the front forks, it's really bouncy. That bike does not work very well if you want to go fast uphill or on the flat. And the reason is because if you imagine yourself on the flat, standing on, sitting on this bike, you can bounce up and down, right? So when you apply force to the pedal, because that's how you get forward on a bicycle, you put force on the pedal and then you move forward. When you put force on that pedal, if the bike is bouncy like it is, you put the force and it just absorbs, right? The bicycle absorbs your force and you just end up bouncing up and down. Of course, you end up going forward as well. But some of the force that you're applying to the pedal are just being absorbed by the bicycle instead of going into the ground essentially and moving it forward. Whereas a road bicycle, which is what the road cyclists use, it's meant to be as stiff as possible because all of the force that you're putting in the pedal or as much of it as possible need to go into moving the wheel forward and essentially down onto the pavement and get the bicycle to move forward. The stiffer the bike, the more of your wattage, the more of your power will go into moving the bike forward instead of being absorbed by the bike. Now enough about bikes. Let's talk about running. The same applies for runners, believe it or not. It's the exact same principle. When you are applying force, remember, it's your muscles applying force. So when you're moving forward, there's a lot of different muscles that are involved. But typically, we're talking about your calf muscles, your quad muscles, your hamstring muscles, your glute muscles, your feet muscles. Most of the muscles are involved in some respect. But let's, for example, talk now about the calf muscle. So the calf muscle contracts and that applies force. Where does that force go? It goes from the muscle via the tendon to the bone, which is then moved and that moves you forward, right? So if we kind of imagine that this is the calf, this is the foot and you're like pushing off going forward, the calf is contracting, which planter flexes the foot and bam, you move forward. You apply that force onto the ground. Now, flexibility is to a large extent tendon-based, meaning it's really how stiff or how flexible is your tendon, okay? Your muscle as well. So your muscle and tendons, if they're very flexible, that means they can stretch, they're elastic. If they're really stiff, then well, then they're not that elastic. And the stiffer the tendon particularly, the stiffer the tendon is, the better your muscular force is transferred to the bone and then moving you forward. Again, another analogy would be if you're trying to pull something, if you imagine a big sled with lots of weight on it and you need to pull it. Now, if you had a rubber band, a big rubber band to pull it, it would be like super flexible. That would be difficult, right? Because you would apply force, pull, but the sled wouldn't move. You would just be pulling the band. Now, if you have a rope on the other hand, which has less elasticity and is very stiff or is fairly stiff, now you apply force and the sled is moving, right? And in the ultimate sense, if you have a metal rod attached to the, like a hook attached to the sled, the slightest movement will actually pull the sled because it's so stiff. You're transferring all that force into moving sled instead of being absorbed by the pull mechanism. Same thing here, if your tendon is too flexible, which is what happens when you're doing a lot of stretching, you actually end up losing a lot of energy and becoming less economical as a runner. So if you want to be economical as a runner, that's a topic for another video, you want to have stiff tendons. We'll talk about how to do that in another video. Does this mean you shouldn't be flexible? Well, actually, there's a sweet spot. Because if you're too flexible, which is what I just explained, you're going to just be very uneconomical. But if you're not flexible enough to go through the full range of motion at the joint, you will not be able to move in an efficient manner. So your hip extension, for example, if I stand out now, hip extension is this movement, getting your leg behind you. If you're very tight here in hip flexors, you won't be able to actually move your leg far enough back to push off and move you forward. So being flexible enough here in the hip flexors is an important element of being a good runner. So you want to be flexible enough to move your legs and body in a smooth and correct way for a runner. So if you're very stiff somewhere, that might be too stiff in terms of mobility. So in a sense, you need mobility and enough flexibility to be able to move through the full range of motion, but not more than that. You want your tendon also to be very stiff. There's one element which is stiffness, but there's another element which is length. So maybe your tendon is too short. You might want to stretch it through stretching exercises in order to get through the full range of motion. But the tendon material itself should be stiff and this is based on training and genetics, etc., in order for that force to be transferred ideally. So cool topic, I think, is one of my favorite topics. Actually, this book is where I learned a lot about this, an item for runners. I made a review of it. I'll put a link to it there. It talks about a lot of what I'm just talking about today. And so as a runner, are you stiff enough? That's the question you should ask yourself, not flexible enough. So do you need to do stretching? Again, a topic for another video. Thanks for watching. Please subscribe if you want more videos like this on similar topics. Check out some of our other videos. We have a few of them now. I hope you're having a great day. Let me know in the comments what you think about this topic. Are you stiff? Are you flexible? How does it affect your running? I'd love to hear about it. I hope you're having a great day. Bye now.