There are 4 things slowing you down when you start your ride: gravity from the weight of you and your bike, aerodynamic drag from you cdA and air resistance, rolling resistance from the tires (or friction), and of course braking. Some of these are trade-off, where improving one problem will make the other worse. Some can’t be fixed at all. Some problems are bigger than others. Listen in as we discuss how you can reduce external forces and improve your performance.
Dr Will O'Connor 00:07
Welcome to Episode 92 of the performance advantage podcast where we bring sports science to the people with myself. Dr. Will O'Connor and Dr. Matt Miller aka MTB PhD, we're both sports scientists with oodles of experience within the field of applying sport science, to the real world of mountain bike, triathlon, ultra-endurance trail running, track cycling. And everything in between. What we like to do on this podcast is bring sports science to the people. And today, we're going to touch on the four things that are slowing you down. And there, there are a plethora of things that actually slowing you down. But these, according to Mr. MTB PhD, are going to be some of the most important nemeses that you're going to face. So on this podcast, we're gonna get into that
Dr Matt Miller 01:10
right. So I've been like writing this article. It I guess, the reason why I wanted to write this, it's just gonna go on my blog, as I get kind of annoyed.
Dr Will O'Connor 01:22
As generally why you write articles.
Dr Matt Miller 01:24
Do you think Is that why you write them?
Dr Will O'Connor 01:29
Yeah, I think so. I'll get I'll read something, either a blog, or an Instagram posts, or I'll get a question over whatever, platform and I'm like, Oh, I just need to, I need to break this down.
Dr Matt Miller 01:48
Yeah, yeah. I guess when I say annoyed, I'm not like angrily typing 3000 words in the morning, just like, I'm totally blacked out from everything else, because I'm mad. It's just like, You know what, like, I think we need to be able to explain this. Because like, especially with this article, it's, I'm seeing people talk about these marginal, like, extremely marginal gains, when actually there's bigger things that we can be focusing on, we can get way more like performance gains, versus focusing on these tiny, tiny little things. So if we, the point of this article was to bring everything in and talk about at one time to see how big like, one thing slowing you down compares to another thing slowing you down. Because as you say, like there's a lot of forces slowing us down.
Dr Will O'Connor 02:34
Yeah, I think the other thing I write blogs like this for these more science based ones is the you go, someone asks you a question or something. And then you have a look, you just do a quick Google to send them something like Oh, no one's really explained this. Collectively. Yeah. That kind of man, the one that annoys me the most is why you should slow down. No, slowing down just makes you feel better. And you can train more consistently, you know, evil. What's the science anyway?
Dr Matt Miller 03:07
Yeah, well, you know, that is one of the problems because when I showed you this article, oh, that's pretty technical. Well, cool. I could just write it super basic, and then I wouldn't be MTB science, right. So I'm sure people have talked about these. Like, I call them the portrayal nemeses. I'm sure someone's written about these things, but without that little extra explanation. I guess we're not talking science, right.
So what are they? Okay,
Dr Matt Miller 03:38
so I got four things. If you know, like a fifth one or sixth lawn or something, let me know. But I got, let me scroll through this. Do you want to do a drumroll? Now or it is not that big of a deal? I'll try. Okay, that's not a drumroll. But that's okay. We got gravity, right. Gravity is one thing slowing us down. Another one is aerodynamic drag. Or you could call it air resistance, I'll probably use the terms interchangeably. We have rolling resistance, which actually, like if we're thinking about a bike, we're thinking rolling resistance, everything about runners, we're probably thinking friction. Or, yeah, would you call it something else when you're talking about running like the contact between your shoes in the ground? Ground contact time, ground contact time. Okay,
Dr Will O'Connor 04:30
it's it's one of those terms, that probably covers like three different things, you know, because it can be specific to the shoe. So if you had a really heavy trainer, it would absorb a lot with not a lot of recoil. So to increase ground contact time, then But then if you had that, like no shoes on this, essentially Nothing absorbing, you know, there's no cushion underneath absorbing any of your forces. But you were running in mud, you'd have a really long ground contact time.
Dr Matt Miller 05:10
Interesting that is slightly different than this. I'm thinking you're running with trail running shoes on the track
Dr Will O'Connor 05:19
come, that's another thing. So that would be the third one. Right? So you kind of have three different points.
Dr Matt Miller 05:28
Of all related, I'm going to actually write that down three things related to one metric. Okay, hold on, I'm making a note three things.
Dr Will O'Connor 05:35
But you I mean, rolling resistance can be your tire or the it's the same, right? Because you can have, you can have the pressure, like the air pressure, and the tire, because you had flat tires. Or you could have the tire itself. Or you could have the ground the tires rolling on. Yeah, it's the same thing, right?
Dr Matt Miller 06:02
ground contact time is a little bit different. That's probably actually as closely related to braking, which is the fourth trail nemesis. It wouldn't be you it's the
Dr Will O'Connor 06:13
biggest the big difference, right? As you as a cyclist, you have continuous contact with the ground. Yeah, runners barely contact the ground. I mean, the difference what differentiates running from walking is flight. Is the point at which there is no, there's no contact with the ground. Yeah. Because of your race walking, you leave the ground you are now you get a red flag, or I
Dr Matt Miller 06:41
can be classified like lumbering. That's what I'd say. And I'm lumbering around the forest, or I'm in contact with the ground. But I look like my body. It looks like it's running. Now, actually, I'm getting better. I'm getting better at running. I've been running every week.
Dr Will O'Connor 06:57
It's like everyone at the end of an ultra. I'm running. Like, well, I can see both your feet on the ground. Like you're doing the motion of running. But what you're doing is walking. Yeah.
Dr Matt Miller 07:10
It wouldn't at that point. I think it's like, it's like, do I walk or do I run? And like either one hurts?
Dr Will O'Connor 07:17
Yeah. How do you just do what you do to move forward?
Dr Matt Miller 07:21
Yeah, just just get there. Okay, so we got rolling resistance, which maybe not totally like. Okay, well, we'll have to cover that another time. But then we also have braking. Okay, so obviously, I love talking about braking. Actually love talking about all these things. I wouldn't consider myself an expert on rolling resistance over aerodynamic drag, just because I think they're so tiny, which is going to be kind of a theme here when we're talking about these four trail MCs. So gravity, aerodynamics, rolling resistance and braking, the four things slowing you down. And when I think about these, I'm thinking about them in a loop, right. So you, you leave, let's say on a bike or on when you're running, you leave the car or your house, you go and you go up the hill, and you go down a hill, and you come back. And you might do that multiple times. Or you might do that only one time. And you might go all different places. But these four trail nemeses are all slowing you down at different points along that loop. And sometimes it's a trade off by where if you improve one, you're making the other worse. And some you can't fix at all. Some you can maybe throw money at the problem and make it a little bit better. You know, like a weight weenie or something, you just buy something a little bit lighter, but then that's a trade off for something else. And then others are like something is something that you're actually doing, and you're in control of it. And you can actually fix it.
Dr Will O'Connor 08:49
So okay, so I'm Yeah, standing on the start line or getting ready to my my training
Dr Matt Miller 08:57
in the car and you're about to like hit Go on your gun. Yeah,
Dr Will O'Connor 09:00
got an hour. And I'm going in back of the car. And what's what's happening? Like, what? Why am I sliding down?
Dr Matt Miller 09:11
Well, I'll tell you why you're not moving. Well, firstly, I guess it's inertia. But gravity. Gravity is probably the biggest one. You know, gravity is acting on us all the time. It's what's keeping you you glued to the ground? Yeah. When you're at the end of an ultra lumbering and he's not right, either. Yeah. So the whole what you have to do is you have to fight gravity.
Dr Will O'Connor 09:38
Okay, right. Yep.
Dr Matt Miller 09:41
Gravity is number one. And actually like this is, is a huge force that we have to overcome to maybe get up a hill. Right. And we know that if we've ever, like, left the car and gone up a hill, like it's hard work yet so you could push harder. that'll get you out faster. But the kind of the work that you have to do is related to the size of the hill and how heavy you are.
Dr Will O'Connor 10:09
So if gravity is a constant as at 9.81 meters per second squared, yes. Why is it harder to go up a hill has the same gravity?
Dr Matt Miller 10:22
Why is it harder to go up a hill? Wow, that's like, such a basic question. But yeah, right. Okay. Because like to, to overcome to, uh, to get up the hill, we have to produce work with our muscles. Yeah, right. So that's measured in joules. Now, we can calculate how much work it takes to go up a hill, based on how, how much vert we're gaining, and how much we weigh. Right. So that's a set amount of work. Yeah. So if you weigh 100 kgs, and you're going up 100 meter Hill. Yeah. Okay. Now we're actually starting to talk about bigger numbers, but it's gonna take a lot of a lot of work. A lot of jewels to get you there. So you do. Dana J. Yeah. 100 meters times 100 kgs. times 9.81. Okay. Yeah, there's a lot. Like that's a lot of work. Obviously, like, you can do that really slowly. Right. So if you go up a hill slowly, it's not that hard. Right. Like if you walk up a hill, yeah,
Dr Will O'Connor 11:30
sure. I mean, it's all relative. But for the sake of we got a good amount of fitness. It's, it's fine. Yeah, it's it's not that hard. Like, the staff is themed. Yep.
Dr Matt Miller 11:42
Yeah, I mean, now we're starting to talk about fatigue, which obviously slows you down. I didn't put that in there as one of the four trail nemesis. So maybe that's number five. But it is like related a little bit differently.
Dr Will O'Connor 11:53
So you're not really you're not talking about physiological components. He talking about external forces? That's right. Yeah.
Dr Matt Miller 12:00
Yeah. So you got the hill, and it's a certain amount of work to go up the hill. So it doesn't matter. Like if you go fast, or you go slow. The the work required to get up this hill is set. Yeah. So that's the mass times gravity times the height. Okay. So it doesn't feel hard until you start to go faster. Right, so you have that set amount of work, and you decrease the time, which means your power goes up, because powers work divided by time. So our muscles kind of, you know, they get tired when we have to do a lot of work really quickly. You talked about that one, we talked about running to the donut shop. Remember that one? Yeah. I can't remember if I got the donut or you got the donut. But maybe we both got the donut.
Dr Will O'Connor 12:47
It was as dependent on Yeah. A lot of things anyway. So. So what you're saying is, it's not actually harder, you're not doing more work is just generally that you're trying to do the work faster. Yeah. And there is a minimum speed at which you need otherwise you just fall off your bike? The Yeah, well, I know it's still hard at because I can do 100 meters on the flat. easy
Dr Matt Miller 13:21
that you can, but I have athletes tell me this all the time, they say I get to a hill and I can't stay under 200 watts. Like you can. And I know you can because if you've ever tried to go up a hill totally blown. You're going at less than 200. You know, that's your your endurance pace. Like if you're totally blown. And you can't like get even close to your threshold. You're going at 200 watts.
Dr Will O'Connor 13:48
You got like usually rpm and the like, yeah, yeah,
Dr Matt Miller 13:52
I tried it the other day. I was like, totally blown from doing these hills as like, I was having a hard time staying under 200 Watts, right. And I've been getting this zone creep where my zone keeps like, suddenly my zone two becomes on three. That's yeah, a thing that we say you shouldn't do. I'm doing that. And like, wow, it actually I don't think I can stay under 200 watts here. And when I was tired I sure could. Right. So I was like yeah, okay, forget it, Matt. But yeah, so. But gravity is what causes that, like, you can ride at 100 watts on the flat, but gravity isn't really a huge factor that you have to overcome.
Dr Will O'Connor 14:35
You have to know especially not on a bike because you're being held up.
Dr Matt Miller 14:39
Yeah, like you runners would have to overcome gravity on flat like Yeah,
Dr Will O'Connor 14:45
yeah, so like it's, you can hold a constant pace when you start a hill or effort I should say quite easily, especially if you're running to heart rate or power because You're already fighting gravity every time you lift off the ground, and then now, you're still fighting gravity. But you're just you're striving shortens, and you're just not traveling as high. But if you want to maintain pace, I think part of it is you must be accelerating against a downward accelerating force. Right. So now now you're getting a multiple, it must be to the, to the quad.
Dr Matt Miller 15:27
I'm not sure. Actually, I guess what I'm thinking though, is like when you're doing that, like a one way to make it easier is to be lighter. Right, since, like the, the work required overcome, well, we can calculate what the work that we would need to do mass times gravity times height, so we can't reduce gravity. And the height might be set. So that's when you're running. Like you're raising your center of mass, certain height, or you're going up a hill that is a certain height, but you can change mass, right. And that's by being lighter. So then you have to produce less power to go the same speed, because you don't have to do as much work. Yeah. Right. So when I'm thinking about these trail, nemeses, I'm thinking about weight weenies that are trying to make things as light as possible. Yeah,
Dr Will O'Connor 16:15
makes sense. So what that does is one of the variables that is contributing to their absolute number. So yeah,
Dr Matt Miller 16:22
it does make sense. Like so. But we did like this whole episode on bike weight. Like why bike weight doesn't matter? Yang's like that. And it's consequentially borrowed that article. And
Dr Will O'Connor 16:38
not by us.
Dr Matt Miller 16:42
Yeah, so like, you can you can kind of throw money at this problem of having to fight gravity to a certain extent, but then it's like a trade off where like, how, how light Do you want to be like, if you go for a run? And you're like, Yeah, I'm not gonna take water, which I know you did not long ago. And it was really hot. Like, I can run real fast, because suddenly, I don't have to fight gravity as much. Yeah, now I'm thirsty. Right. And same with your bike, you can put on lighter tires, or you could put on super lightweight handlebars that are potentially going to break. Like, well, there's actually not a ton of time that you can gain up this pretty long hill, just by, you know, saving 300 grams or something like that is not a huge deal. So sometimes that trade offs not worth it. So that's mostly what we talked about in that episode. But like, I think the example I gave from Palmach Dr. Paul McDermott's study was you can save one second up to two and a half minute climb by saving 335 grams. So
Dr Will O'Connor 17:42
yeah, I have to pull out some of the articles on running because they, they really done as they, it's hard to really to do it and run him because you can't just add weight to like a bike, you know, which is constant, but they did use sand vests and showed your general running pace economy was maintained for like a few kgs. But this is saying, you know, these these sayings, but it's like one kg of body weight is worth one minute for tea over 10 kg. And so someone I mentioned who, within our department, you say that to me? And I was like, that just doesn't even make sense. Like, otherwise, you know? It just it's just yeah.
Dr Matt Miller 18:30
Right? Like, how much do you weigh economy though, is like how its work per liter of oxygen, right? So if you suddenly have to do more work, because you weigh more, well, you're just going to go slower. It's not going to change how much oxygen you need. So economy, you wouldn't expect to change. But obviously, you'd be going slower. So that's really what you want is to like not go slower.
Dr Will O'Connor 18:57
You want to not go site. So just by losing weight as well doesn't necessarily mean you're like because you can get a greater appreciation of you know, the law league spring, which could increase recoil, like, if two of you know there may be kg either way, and which economy is not affected? Because you can compensate through the return of energy, which is gained, you know, at all like, like, where is where is that? Wait, where have you lost them? Yeah, right. Right. Right. Because it's like, dude, white is very different than, you know, I've got like, no body fat. So if I'm losing it on, I could potentially be losing functional muscle. Right? And that may just be negligible.
Dr Matt Miller 19:49
Yeah, yeah. So like, I guess when I think about weight, I think like, it's obviously super important, but you can't go to extremes, because then something's just Gonna go wrong, whether it's with your body or with your equipment.
Dr Will O'Connor 20:03
Yeah, Shoes Shoes are the same, because you can they sit at the bottom in the pendulum, you know, which is your law alum. So I mean, that's a very different place to have weight then and on your shoulders, say or like a handheld 30 mil bottle of water. But then yeah, what are they? But then you say you just run and be your feet and you get injured.
Dr Matt Miller 20:28
Exactly like that. That's an extreme, that doesn't make sense. Like you wouldn't do it. So, okay, we, we talked about weight, at length. So obviously, it's big, but just be careful. And that's kind of what I'd say is like, it's a huge thing slowing you down, be careful. So then we got this thing, aerodynamic drag, which I'm going to try and fumble my way through.
Dr Will O'Connor 20:52
But it's with gravity, it's constant. As well, like it's true, like, always gonna be there. But it's gonna I have these, these athletes are both doing the same race next weekend. And there's, if you know, Mount Maunganui, there's like the bass track, you know, which is undulating trail. And it's only about two and a half kilometers long. So what's that met like a one and a half miles of he do it twice as part of the half marathon, just like 13 Miles 21 case. So it's, it's like nothing in as like that I was going to be such slow course. I was like, well, you're actually like, you're only going to go slow on the oppose. And the apples are only going to be about a total of 5% of the entire race. And then you have a downhole as well. Right? So in the end, like you have what is it is going to be a slower section and if you're just on the flat pavement but it's not the be all and end all of like, a completely Yeah, throw away race, it is never gonna be news, it never has the potential to be fast. Because your while you have to go slower in terms of its, you know, in terms of PACE speed, because you've got to find the fixer gravity greater when you're traveling towards it. I guess. You give it on return on the down
Dr Matt Miller 22:29
gravity becomes your friend. Yeah. Yeah, it's,
Dr Will O'Connor 22:33
it's constant. So yeah, I think we yeah, we do think about these things as like, Ah, this is a you know, this is big uphill. And for mountain biking, especially. These this big downhill, which has this huge potential to be able to gain considerable amounts of time. If you, you know, took care of the fix of gravity on the way up.
Dr Matt Miller 22:59
Yeah. Yeah. Yeah.
Dr Will O'Connor 23:04
And Dr. Dynamics, yeah. Okay, so should we think about aerodynamics?
Dr Matt Miller 23:08
Um, they probably should, though. Why would they not think about aerodynamics?
Dr Will O'Connor 23:14
I think about this, because these, these are quite a few runners have long hear short distance runners, and hairy legs to German. But in this 2000 Sydney Olympics, Cathy Freeman, had the full body suit.
Dr Matt Miller 23:32
It headachy don't remember it.
Dr Will O'Connor 23:34
She's all men. Now I'm going to test myself with her. She's a 400 or 800 or both things. She went gold in both. And she had like the, like, full ankle to
Dr Matt Miller 23:48
do remember. There were a few people trying that. And they tried the same thing and downhill mountain biking, where, like everyone was rocking lycra, which just looks ridiculous. Like they had skin suits. Yeah, I'm gonna tell they got banned. They got like, because it didn't look cool. Which might be what happened in like track running. Because like, you know, lycra is cool, but if you don't wear lycra regularly, you don't think that looks cool. You're not
Dr Will O'Connor 24:18
a you know that. They're called, you know, gimp suits if you're buying them for a dress up party. Yeah, and that like no one wants to see that. No, like, you can't just you can't wait if it's not. It creates a pretty large shift in trend like tradition to just be seen like running shorts and a singlet vest to like a full on. lycra suit.
Dr Matt Miller 24:53
Well, you know, downhills kind of gone that way, right. So they went from full on lycra, were like obviously there Going at really high speeds or aerodynamics is really important. And they went to like just crazy baggy stuff in the early 2000s. Or, you know, when we wore shorts down to our ankles, and like three sizes too big tops, and there's just flapping in the wind, like that actually is slower.
Dr Will O'Connor 25:16
So because I asked I think I asked you about this a while back, is that why they're wearing such baggy clothes? You said they gotta have like two fingers.
Dr Matt Miller 25:24
Distance Yeah, I'm
Dr Will O'Connor 25:26
not sure like the rule is skin and the clothing Yeah, I I'm not sure actually that would that sounds like a UCI ro.
Dr Matt Miller 25:36
Sock length thing.
Dr Will O'Connor 25:38
Yeah, good cough
Dr Matt Miller 25:41
yeah yeah, I'm not sure what the rules are but like obviously there's this fine line between a nice look cool and we want to go fast. So there's, they're like kind of
Dr Will O'Connor 25:52
a fine line. This shouldn't be this shouldn't be right. Like it should just be we need to go fast. That's the goal.
Dr Matt Miller 25:59
Like yes, well, that's why like you see down there's now tucking in their shirts where they didn't really do that before. They're just like, let's look as cool as possible which means as baggy as possible, probably wearing Dickies. You know, that that's like an era thing. fashion. But now it's like a little bit tighter. Obviously, they know they're going really high speeds pants or like skinny jeans kind of thing. But so this is this is what kind of brings me to aerodynamics is like, well, how important is it? Because now we're seeing the advent of these. I'm not sure what you'd call them. These do hickeys that measure your frontal area and try and estimate like how aero you are at any given time. Have you seen those?
Dr Will O'Connor 26:45
Yeah, these? Well, this is the what are they called? What are the things on the aeroplane that is measuring aerodynamic drag?
Dr Matt Miller 26:57
Actually, I'm not sure what they're called. They're like these little wind flappy things. They're tiny little.
Dr Will O'Connor 27:02
So not even flappy. They're just a nozzle.
Dr Matt Miller 27:06
Yeah, well, there's like a read kind of thing. Almost like, what's inside of a saxophone? Yeah. So.
Dr Will O'Connor 27:15
And, but, yeah, they've been trying to make those for, especially for time trial bikes.
Dr Matt Miller 27:22
There's a bunch of companies making them now. And, yeah, they're expensive. And like, you need the app. And I think some of them now read onto your Garmin or something like,
Dr Will O'Connor 27:32
yeah, you got to control a lot. Yeah, because if you're not controlling between measurements, it's like, what? What are you measuring?
Dr Matt Miller 27:44
Yeah, I guess like I have to be in the same position. So what these things I do, like they know what your power is. But they're essentially trying to measure your frontal area, because this is what's hitting the wind is your frontal area. And you might see it written CDA, which is your effectively that's what they're the notation is in the equation for your frontal area. And that's what these so if you know your power, and you know your speed, then you can kind of estimate your frontal area. So then, you know, if I put go in my drops, or if I use this arrow bike, how much more Watts am I gaining? Yeah, right. So it's, it's negligible. It's like a few watts, like a few seconds in a 40k. TT, when you're already Super Arrow, like getting more arrow isn't going to make you go that much faster. So I looked into it, then this is where I started to look at some, like real science that I did a few years ago, where we're measuring braking, we're estimating all these things like rolling resistance, and aerodynamic drag. And we're measuring like how much these were actually slowing you down. At any given time. We had like, hundreds and hundreds of measurements. And then we estimated aerodynamic drag, and rolling resistance for every single short section of a rod. Right. So in the end, we estimated that you're losing 17 Watts to drag. Wow, that was for like a normal sized person riding on a mountain bike. So 17 Watts, drag at 42. Just 17 watts. So anytime you're moving. Yeah, drag slowing you down. All right, right. Through the year. Yeah, yeah. So if you're
Dr Will O'Connor 29:34
traveling for all other things being constant in your aerodynamic drag is going to cost you 17 watts.
Dr Matt Miller 29:45
Yeah. So if you take one pedal stroke, away from your car to go do this loop, and then you stop pedaling, you're going to eventually come to a stop even on flat ground. So this is where the everything else is acting against you. So gravity is fighting against you or die. MC drags fighting against you rolling resistance is fighting against you. You don't even touch your brakes, you just come to a stop. Yeah, right. And then you make sure you don't tip over. Because that's when you got to worry about tipping over. So drag is slowing you down. And that's just one of the reasons we have to pedal. Right? So we have to pedal to continue to overcome drag, the faster we go, the more aerodynamics becomes important.
Dr Will O'Connor 30:26
Dr Matt Miller 30:28
Yeah. So like, if you're not going fast, like if you're going up a climb, the main thing you have to find is gravity. Yeah. Right, because you're going so slow that air resistance is relatively small. But in the the numbers that we calculated, the average speed was about 14 kilometers per hour. And at that speed on mountain bike with, you know, kind of sitting upright, you're losing 17 watts.
Dr Will O'Connor 30:55
So as velocity squared, like, why is the increasing? Like, aerodynamic drag increases with speed? Yes. Yeah. Why? Is it due to the density of here? And as you move, as you increase your speed, you're having to, I guess, like, are you hitting the dense? Like, new air? Faster?
Dr Matt Miller 31:34
I guess? Like I didn't the most simple way to think of it, you can think about it as you're hitting more air. per unit time. Yeah, sure. So you're like slicing through more air?
Dr Will O'Connor 31:45
Yes. So Oh, air, Oh, I gotcha. So resistant, because it's, you're kind of accelerating into the density. Right. So it's kind of no different than gravity, which is squared, as well. So if you're going to accelerate into a downward accelerating force, it's going to be a multiple,
Dr Matt Miller 32:10
I'm not sure if that's the right way to think about it. But the equation is like, you multiply your frontal area times the air density, times velocity squared, times your distance, and then you multiply that by point five. So it's like a kind of complicated equation. But I think that doesn't matter. Like we're never going to go out there and calculate aerodynamic drag, what we essentially need to know is that it's always acting on us, the faster we go, the more it matters. And we're always going to be losing energy to drag. So 17 Watts and 14 case per hour, we let's just think about it like that. All we can do is potentially lose maybe 16 Watts, right? Or 15 Watts, you know, or maybe 10 Watts, or something like that. We're just not a considerable difference.
Dr Will O'Connor 33:08
Ever thought about it was a long night. I did some intervals that day. Last night, right. And I had one minute at 415 watts. And then, I was pretty guessed, and then I had a minute and a half at 410. I was like, that's like the same thing. It's not. You know, like, at that point in that could
Dr Matt Miller 33:39
have been a warm up or something was effect.
Dr Will O'Connor 33:42
Not. But then if it was 150, this 155, same, same. You know, because we were like, That's me operating. It's like, I can't remember like 140 150% of my FTP. So those small incremental increases and resistances. Like, is feels exponentially harder than, like, what is on the
Dr Matt Miller 34:13
I mean, five watts out of 400. That's within the error that you'd expect from the device that well within the error that you'd expect. Like, that's tiny. It's a tiny,
Dr Will O'Connor 34:24
those errors out one to 2%. Say that's like, well within slack,
Dr Matt Miller 34:30
it's within one to 2%
Dr Will O'Connor 34:33
Dr Matt Miller 34:36
Okay, so, I mean, yeah, so if you were like, I don't
Dr Will O'Connor 34:41
think you can just throw like I'm not just throwing away five watts I could love there.
Dr Matt Miller 34:48
Yeah, okay, that's a that is a great point. But I think the main point here is like you're never going to get aerodynamic drag to zero. So we see people like in the mountain bike world cup like pretty their hands way down on their, like the top of their fork, which is like totally inefficient and uncomfortable and not to mention extremely unsafe way to ride a bike. I have a photo of you trying it is like a long time ago, I
Dr Will O'Connor 35:15
saw it the other day. It's sketchy man, it looks ridiculous. It's ge, you don't hear any control, no control,
Dr Matt Miller 35:22
and you're potentially more arrow. But like, what are you going to crash? Like, if you're on the ground, like you're going way slower than the one watt that you saved?
Dr Will O'Connor 35:33
I actually like how you justified that it may be more error, because specialized writers were doing it and they had the specialized wind tunnel to like maybe they didn't test it. Like how you justify that this is something they interviewed someone I at the Tour Dubai as one of the great British writers. And it was after the 2012 Olympics. And it was like, you know, no socks? Do you think they should do it? Because they said the British team wore no socks and they wore them at the World Championships in the lead up. Everyone was like, Oh, my God news, you know, because they were that marginal gains gurus. And anyway, then the guy just said, because it was a couple years later, you know? 2014. So it's like, oh, now we just did that to mess with everyone. It didn't make any difference at all. Yeah.
Dr Matt Miller 36:28
Right. I mean, even if you can just
Dr Will O'Connor 36:32
but people like if you're at the top end, people like that must be faster, because there's no way someone would one way or no socks and look that ridiculous. Or to take the risk to put their hands on their foot. Yeah, crowns to like, if you just
Dr Matt Miller 36:51
right. I mean, there's a perfect example of why we're talking about this now. Because, okay, if you can, if you're at losing 17 months, let's just say you losing 17 Watts, if you could potentially lose only 16 watts by wearing no socks, like do you really think like, that's like the main thing, when every all these other things are hitting the wind, and you're only losing 17 watts. Like to be to be perfectly clear, 17 Watts is not much like that is you lifting up something that weighs? Was 17 grams, or whatever up a meter?
Dr Will O'Connor 37:31
Well, it's always gonna be there. Like, it's never going to be zero. I think there's the, that's an important point. So it's not like you can take your socks off, and now you're like, you've just saved 17 watts.
Dr Matt Miller 37:42
Exactly. So you make one watt here and there. But it's always gonna be there, right? Because you are slicing through the wind. So it's tiny. is kind of the whole point. Like, don't fuss too much about aerodynamics, especially if you're like taking other people's lives in your hands to do it.
Dr Will O'Connor 38:07
Okay. To a point, it all happens to a point.
Dr Matt Miller 38:13
Okay? Yes, but let's keep
Dr Will O'Connor 38:18
thinking about triathlon. Like, if you don't have a time trial bike, you can't stay in the aerodynamic, you know, talk on your aerobars. And that makes a huge difference can drastically reduce your frontal area by having aero bars?
Dr Matt Miller 38:36
Yep, totally agree. Plus, you're going really fast. And that's when it actually matters. Like if you're averaging 40 case per hour, obviously, the energy you're losing to drag exponentially increases. So that's when it really starts to matter. When you're running, maybe it doesn't actually matter, because you're going pretty slow. When you're mountain biking up a hill, it probably doesn't matter. But when you start to go really, really fast, it actually does. And that's kind of the the other point. It's like, well, it's small, but it only matters when you're going fast. Yeah. Okay, so I don't want to like make it seem like aerodynamics is nothing but compared to these other things. It is.
Dr Will O'Connor 39:25
What other things Okay,
Dr Matt Miller 39:27
rolling assistance. Yeah, next we got rolling resistance. So,
Dr Will O'Connor 39:32
so we're going to use 19 mil tires at 120 psi.
Dr Matt Miller 39:39
I don't think that's cool anymore. That used to be cool. I know. I probably mentioned it before, but I had like this continental I don't even know what they were called then. But it was like a skinnier front one and a fatter back one. I think the front was like it might have been a 17 or something in the back what was in 19? Yeah, pump it up to 140 Like, I'm sure there's a lot of potholes around here, I run my mountain bike tires at like 17. But like, luckily, I don't think anyone's actually doing that anymore. With the super pumped up tires to I don't know what the goal was, was the goal there to like reduce rolling resistance.
Dr Will O'Connor 40:20
Yeah, it was because when I started triathlon and I got some carbon wheels now like, highest possible one, I tubulars now like our tubular zoom, do way higher
Dr Matt Miller 40:35
what I thought the point of tubulars was to go lower.
Dr Will O'Connor 40:39
Well, who cares? I had them at 140 and I was bouncing all over the New Zealand roads. Yeah, you're like big chip. And then then it slowly started transitioning from Yeah, like a 1921 no tire at 142 like a 25 Maybe even the 28 for longer distance it depends on the to like 90 There's a massive difference. I remember just putting 25 bills on since the what the attire and and running them at a law pressure being Wow. Like that is so much more comfortable. Yeah. Like I'm way more constant on my like speed and power output. Because I wasn't literally bouncing all over the
Dr Matt Miller 41:31
road. Yeah, yeah. I just kind of imagining someone running like harder running shoes. Like skinny hard running shoes, just because I think it might be fast or something.
Dr Will O'Connor 41:44
What is it? Sprint is day. All right.
Dr Matt Miller 41:48
Well, it's shorter
Dr Will O'Connor 41:49
than some what that the fan of the
Dr Matt Miller 41:52
they also were spikes, which I always thought was weird. Because like you actually are digging into the ground. Can't remember if we talked about
Dr Will O'Connor 42:00
Yeah, we did. We did. You just won't. You will not get the traction trying to run like 60 K's an hour.
Dr Matt Miller 42:07
Yeah, maybe for accelerating I guess. Yeah. But for like running a 5k. Do they still were spikes?
Dr Will O'Connor 42:13
Store spikes? Yeah, they're still running. 2526 K's an hour around a bend.
Dr Matt Miller 42:23
Steady, though. I don't know. Like I always we talked about this.
Dr Will O'Connor 42:26
It's you know, when you're on the ground settling 180 290 milliseconds.
Dr Matt Miller 42:36
Yeah, I just I guess I kind of don't buy it. Yeah, cuz if you think about like the Road Runner, the way the Road Runner runs, like spinning wheels, almost. It's essentially how you're running Catone. Yeah, but this is essentially how you're running. Right? There's just like, hey, it
Dr Will O'Connor 42:51
the point of contact is so so small. Right for moving body that needs to apply force. It's just so much I think I think you're thinking about it in terms of a bike and trying to translate that to a run. But you got to run around the corner. Fast. Like really fast. Yeah. See how fast Yeah.
Dr Matt Miller 43:21
Okay, that's fine. But
Dr Will O'Connor 43:23
we need to get an odd brought that down. Get an expert on? Yeah.
Dr Matt Miller 43:27
Okay. Sounds good. All right. So for rolling resistance when we're thinking about the tar. So if we extrapolate these numbers from the same exact data set, what we'll see is that anytime we're rolling, we're losing energy to this rolling resistance. And what's happening is the tires or your shoes or whatever, are in contact with the ground, and the energy becomes noise, or they kind of fall apart a little bit. It's called fracture of the tire. So that energy the ground underneath you. Yes,
Dr Will O'Connor 44:01
like if you're on gravel or something in a displaces. You displaced it?
Dr Matt Miller 44:06
Yep. Yep, yep, exactly. So that that energy loss to rolling resistance can be calculated by mass, which is you and your bike times gravity times this rolling resistance constant, which you can kind of calculate there's actually a few calculators online where you can calculate this mew value, which is like a constant for your tire. Which is pretty cool. So you can see like maybe which tire you might lose less energy to, which again, this one's a trade off. This one's a trade off.
Dr Will O'Connor 44:39
Where do they get into you mute from?
Dr Matt Miller 44:43
Well, what we did with for our dataset is we used a new value from study by ber Tukey I think it's for 2003 study. And then we just use that as a constant in the tires that we were using,
Dr Will O'Connor 44:57
but where are they getting their constant from?
Dr Matt Miller 44:59
They did this test with a ton of different tires. I think what and you'll see it like close to a base the constant offers. Yeah, well, you can do that if you have like a big roll. It's like a gigantic rolling drum. And if that's rolling at a certain speed, you know the energy. And then you can kind of see how the wheels are. I'm out of the tire. Yeah, yeah. Which is pretty cool. And yeah, there are people doing like you, we should probably get someone that does those kind of studies on as well, because it's, it's pretty neat. Like all this rolling resistance stuff. But yeah, so we just use the constant. And what I, again, I extrapolated a bit of this data, but you're losing about 40 Watts, or sorry, 68 watts. About 68 watts. There's, so that's using our data set. So it's approximately 14 case per hour.
Dr Will O'Connor 45:57
40 ways to audit 40 Watts every meter 68 joules every second or so. Yeah,
Dr Matt Miller 46:03
so 68 watts. Because basically to calculate the energy loss, wrong resistance, it's done per meter, actually, and then I worked it back.
Dr Will O'Connor 46:14
Okay, two joules. Yeah, gotcha. Okay.
Dr Matt Miller 46:20
So that's actually a lot. And the point here is that that's like, what is it four times? Four times your aerodynamic drag? Yeah. So is a huge amount, like compared to aerodynamic drag? Like you always hear people talking about aerodynamics. But you don't often hear much about like trying to optimize rolling resistance. And that could be because like, it is a trade off. So I can reduce my rolling resistance down to extremely low by running like slicks. I'm not and then it's probably not 120 psi. On 90 mil tires, it's somewhere something maybe it is a 2590 psi. And what actually ends up making more of a difference isn't the tread pattern, especially on road tires. It's the compound used. So there's an optimal kind of compound that can be used those little kind of lines that are in it. don't really do much for rolling resistance. Yeah. Okay. And then on a mountain bike, it is a little bit similar, where a lot of it has to do with compound use. It's a real soft rubber. They were also slow.
Dr Will O'Connor 47:28
Yeah, man, nice. Tires are so slow.
Dr Matt Miller 47:31
You will I did a study while many experiment looking at comparing tires. So I had these XC tires on versus downhill tires, and wrote up the hill at a controlled power. Yeah, lost. I lost a minute, like using XC race tires versus downhill tires of a 13 minute climb. Yeah, it's a lot. That is a lot.
Dr Will O'Connor 47:52
It's a lot long, like it was my stand to sane.
Dr Matt Miller 47:56
Yeah, it's, it's a bit. So like, obviously, if you're racing up a hill, you you want the Z tires. But if you're racing downhill, you probably want the downhill tires.
Dr Will O'Connor 48:11
Yeah. So when I tell you what, because you got me to put those downhill tires on my bike. Just because you know, I'm not racing. And the grip is phenomenal. You know, it's out of this world. It'd be like, you right, like, next time I put xe tires onto right up there. I'll be like, Wow,
Dr Matt Miller 48:30
yeah, it feels so different. Because I go back and forth. And we'll actually measured the how the tires go downhill to. And I compare these exact same tires on the exact same descent. And I was almost as fast with the Z tires on, they felt a lot. sketchier Yes, because you pick up some speed so quickly, because there's, like, minimal rolling resistance. As soon as you let off the brakes. Yeah, but then you can't slow down very quickly. And so you need to get on the brakes much earlier. So
Dr Will O'Connor 49:01
that was the biggest thing. I noticed. I was like, stop it. I was like, what? Um, yeah. last corner, like real nice. Yeah.
Dr Matt Miller 49:08
Yeah. But yeah, that that is like the trade off then with the tires is Yeah, I can roll faster, but I can't stop as fast. So what do you want to be doing? Do you want to be able to, like, stop really quickly, which obviously helps you go faster when you're going downhill? Or do you want to be able to roll really fast? And obviously, you're not going to use slicks on a mountain bike, because then you won't be able to make a turn. Yeah, so this is
Dr Will O'Connor 49:34
what is possible.
Dr Matt Miller 49:38
I guess I remember I went to sea otter a couple years ago and one of the bike shop. Yes, tried. I was kind of like lurking around with my brake power meter prototype. And one of the guys in the team 10 He I saw him clipping his tires. Like oh, what are you doing? He's like either there's no braking in this course for the downhill. Looks like you just like clipped off all the hops. So there is breaking on the trail guaranteed. And I'm not sure if I'd want to be running slick, he actually had to do it because it didn't quite fit in his frame. So I'm like super concerned, they're running some tracks and new things. But there was there's breaking in that track, you're going so fast, like you'd have to be able to slow down for some of the turns. Yeah. But yeah, I thought that was pretty funny. But I guess rolling resistance is one of those things as well, like, it's always gonna be there. Like even on a road tire, you're going to be losing energy to this rolling resistance. So you can find it or kind of let it be your friend kind of thing.
Dr Will O'Connor 50:47
What about the weight of the tire? You know, because that requires greater inertia. It's kind of like a different weight. Because it's a moving weight than the frame weight. Or like, a water bottle. Or yourself.
Dr Matt Miller 51:07
Yeah, well, the nice thing about inertia, yeah, yeah. Because I think actually, in this paper, with these I sent to you, we had to calculate the inertia of the tire. Because where do i Oh, yeah, it's in equation seven.
Dr Will O'Connor 51:22
Where is this? Open Access? No, but
Dr Matt Miller 51:27
I can put a link to my Research Gate, a link on research game. So like, we have the change in energy, which we're looking at Mass times, half mv v square, but we're also adding in the inertia of the tire, which is related to how fast it's spinning, and the mass and the radius. So radius is pretty important. But with inertia, once it starts rolling, it stays rolling. Right? So if you have a heavier tire, it will tend to want to stay rolling at that same speed. It'll take you longer to get it up to that speed. But it will prefer to stay at that speed because it has more inertia.
Dr Will O'Connor 52:08
Okay, so in a road bike, there probably wouldn't really matter. More. This
Dr Matt Miller 52:11
is why like, cyclists use super heavy aero wheels where because they're going so fast. Aerodynamics is way more important than this. Inc