 Helo, tyngwyr. Rwy'n gwybod am cafin yn cyfafol. Rwy'n gweithio awr ac rwy'n gweithio newydd. Rwy'n gweithio ddim yn gweithio. Rwy'n gweithio cafin. Rwy'n gweithio i'r cafin. Rwy'n charu ffordd ddechrau, ac mae'n byw ddim yn ymddirio i fynd i angen iddyn nhw. Rwy'n cyfafol i'r cafin. Rwy'n gweithio i fynd i'r ddwy. If you have up to about 400mg per day, you can even have a bit more than that, you're not going to have any adverse effects, and I think just to point out initially that that's kind of a fairly typical dose that we would give somebody in a study if we were looking to get an ergogenic response, so somewhere between 300 and 400mg we would give to an athlete when we were testing them. It's a member of a group of compounds called the methylxanthines, and caffeine is a tri-methylxanthine. It's metabolised by the liver, so if you've had some coffee or some tea, your liver is processing that as we speak, and it's broken down to its primary metabolites, which are dimethylxanthines, the main one being parazanthine. It's water and lipid soluble, lipids meaning fats, so that means it can rapidly enter all the cells of our body. We get a peak plasma concentration, so a peak concentration in the blood, about half an hour to an hour after we've ingested some caffeine. That's why when you look at any studies that have been done on caffeine, looking at effects on performance, they will all say that they administered the caffeine round about an hour before they actually test the athlete. So when we're looking to try and improve performance, if athletes are trying to improve performance, that's what they need to do, not take it immediately before exercise, take it about an hour before. It's got a half-life of about four hours, which means that, because of the time it takes the liver to process it, it means that if you have some caffeine, it's going to take four hours for what's in your system for half of that to disappear. So after eight hours, you're still going to have a quarter of the caffeine that you had initially left in your system. My final point there, so if you have more in that time, it's going to add up. So if you're like me and you have a cup of tea first thing in the morning, and then you're travelling to work and you have a cup of coffee, and then maybe a couple of hours later you might have another cup of tea, you can see you keep adding to your caffeine content during the day. Where do we get it from? Lots of places, really. Mostly coffee and tea. Coffee, more in filter coffee than there is in instant coffee. There's a little bit in decaf. They don't remove all of it. It's just not worth the cost of actually getting rid of all of it. So there is a tiny amount, but it's very, very tiny. In tea, it depends how long you have it brewed. If you're like me and weak and milky, you're not going to get too much caffeine. But if you're one of those people, and you know you are, who keep pressing the tea bag on the side of the cup and just doing it around, you're going to get a lot more. Pepsi-Cola, Coca-Cola, and then these so-called energy drinks of course these days that have quite a high content. But even in something like Red Bull, you really need about three cans of Red Bull to get a normal ergogenic effect which I'll come on to in a minute. It's also added to lots of products these days as well. So sometimes you can be ingesting caffeine and not even be aware of it. So the first ergogenic thing I want to look at here is, is there a dose response? So this was a study from a few years ago where they were looking at time to exhaustion. Efectively, they had people running on a treadmill at a speed that would exhaust them in about 50 minutes. In other words, they're running and running until they just can't go anymore. And they found that when they had no caffeine, they lasted about 50 minutes. When they had a 3 milligram or a 6 milligram per kilogram dose, they lasted over an hour. Big change from zero caffeine. When they gave them 9 milligrams per kilogram, it actually dropped off a little bit. They were having nothing, but it seems that it follows this inverted u response. So if you have somewhere between 3 and 6 milligrams per kilogram, you get an optimal effect. So if you're an athlete, this is the dose you really want to be taking. Now these slides, I'm aware, I always say when I'm watching presentations, if I can't read the slides, I say, why have you put this up there? But I don't want you to pay any attention to this apart from realising that there are lots of studies. This is a study that I'm actually writing up at the moment. And this is looking at the effects of caffeine on real performance. So if you're Malfara running a 10K, or if you're Chris Froome in the Tour de France doing a time trial, the only thing I want you to look at is, where has this gone? I've done that same thing. The little pink diamond at the bottom. So this line here is the line of no effect. If that diamond sits that side of the line, it means caffeine is having a positive effect. And if it sits on this side, a negative effect. These are time trial studies. It works. It's a legal supplement and it works. And we get a typical improvement of about 3% on average in performance. So I'm just going to touch on some physiological responses as well. So heart rate. I had this sort of preconception when I started getting into this area that caffeine increased heart rate. And I think most people kind of think the same. If we look at the time trial response, so just when people have done an actual performance, heart rate goes up by about 3 beats per minute. But think back to that previous slide, the working harder, the running faster with caffeine or cycling faster. So the question I had was how much of this is due to the fact that the working harder because of caffeine and how much of it is just a direct stimulatory effect of caffeine on our physiology. So this is a study I did where we got people to exercise. So this is heart rate here and this is incremental exercise to keep it simple. This is somebody exercising at a really low intensity and then a little bit harder, a bit harder, a bit harder and so on. And you can see at every intensity, heart rate goes up. We look what happens with caffeine, it's lower at the lower intensities. And in fact at rest we found that caffeine reduces resting heart rate. And that's there in the literature. There aren't too many studies that have looked at it by about three to four beats per minute. So not a huge difference, but it certainly doesn't increase heart rate, it actually reduces it a bit. When Malfara is doing his time trial, he's working at this end. At this end we don't get any significant change in heart rate as a result of caffeine. If we fix the intensity, so these are studies where in the caffeine condition and the placebo condition they're working at exactly the same intensity. So it's not a performance test, you're running on a treadmill with caffeine or placebo, the intensity is the same. No effect on caffeine. So just like we showed in the upper end of that previous slide, there's no effect of caffeine on heart rate. So what we can say is, if you're doing a time trial you're going to be faster and your heart rate is going to go up. But your heart rate is only going up because you're working harder, not because caffeine is doing anything to your physiology. Now often when we do physiological tests we have a scale that we show people where we say, how hard are you working? And it goes from six to twenty and you say, this is where I am on the scale. If we look at the time trial response, that's pretty much in the middle. There's no effect of caffeine on how hard you think you're working, but remember you're working harder. So you're performing better in the time trial, but you don't think you're working any harder. And if we look at fixed intensity work, so when you're working at the same intensity, you feel it's easier. So caffeine is having this profound effect on how hard you are finding exercise. And that's been shown lots of times and certainly summarised in these meta-analyses. So, yeah. And it's also associated as a mild pain relieving effect of caffeine. And we think that that might be the reason for that response and might also be the reason why we perform better as well. So the last one of the physiological responses I wanted to show you was this one on blood lactate. So if you're not familiar with blood lactate, you may very well have heard TV commentators and athletes talk about lactic acid. And it's generally in tough races and they'll say, oh, his legs are filling up with lactic acid. So this is, we're measuring here blood lactate, which is essentially an indicator of lactic acid concentration. Again, starting off easy, getting harder, harder, harder. That's our placebo response. That's our caffeine response. Same intense to this. These are same intensities. Just getting harder and harder. So caffeine is increasing blood lactic concentration or lactic acid concentration. And that was all the way through the profile. If we look at this range again, so where Mofara's running, if we fix the intensity, then we confirm that previous slide. So at the high end of that previous slide, we see we've got a clear effect of caffeine on lactic acid concentration. So we get an increase of about 0.7 of a millimole per litre. Doesn't matter too much, but it will make more sense when I show you the next slide. When people do a time trial, that value is over double what it was on the previous slide. And again, this is the one I'm working on at the moment. This is the one I'm writing up at the moment. So what we can say here is, unlike heart rates, when you're doing a time trial, you're getting an increase in lactate. Part of it is coming from the increase in intensity, but this time we can say that part of it is also coming from the fact that caffeine is having a physiological effect on us that's causing that lactic acid concentration to increase. And I think the other thing to point out here is performance is going up, lactic acid concentration is going up. You will hear every single TV commentator say people are getting slower because they're cumulating lactic acid. We've known that isn't the case for a long time, we just need to educate our TV commentators and athletes that that's the case. OK, so that was all I wanted to do on endurance exercise and physiological responses. The last few slides I want to talk a bit about sprinting, caffeine and sprinting, because there hasn't been a huge amount of work done on this. So every time I do a study, I search the area and I usually put one of these tables together so I can understand and get a feel for what's going on. So I've got all these studies that had looked at caffeine and some kind of sprinting performance. And I kept reading in review articles people would say the effects of caffeine and sprinting is unclear. And I thought OK, so I put this table together, now how I did them in blue, the responses, all the ones where they showed no effect. So I got all these studies and I was going no effect, no effect. I was like why are people saying that this is unclear? Because to me it seems pretty clear. Now we had one discrepancy here where they showed an increase in peak power, but you can see these same authors did a subsequent study and found no effect. And the reason these review articles were saying it's unclear was this one study by Anselm where they found an increase in peak power, maximum peak power. So I read through this study again and I looked at the sample and I thought well there's 14 participants, that's pretty reasonable in a physiology study. But they had males and females and there can be some issues when you use both from a statistical standpoint. But maybe an issue there, I looked at the dose, they gave a fixed dose rather than a body mass relative dose. So particularly when they got males and females I thought well the females are going to be lighter so it's going to mean they're going to get a heavier dose than the males. I thought OK, an issue there. And then I also looked have they measured blood caffeine concentration. In other words, when the people turned up and they were having the placebo were they really free from caffeine or had they inadvertently had a cup of coffee in the morning or whatever. So I thought there's issues here so we can fix these issues, we'll do this study again, we'll repeat it. And to be honest I thought we will find no effect and we can put the whole idea to bed. So I'll show you what we found. So what we've got here is gradually increasing resistances is the best way to describe it. In other words people are sprinting on a cycle of a gometre for six seconds. There's lots of recovery between each bow but essentially at 0.4 your legs are spinning like mad because there's no resistance. And up at this end you're struggling to turn the pedals around. So what we see is that your peak power output goes up with increasing resistances to this point where it starts to level off and then it would then start to dive away. If we look at the caffeine, well it doesn't have as much happening until we get to this end and it looks like there's a bit of a divergence going on. So if I take those two lines off and we just focus on the peak power output, so the best power output they did which was right up at this end, we found there was a significant difference. We found there is an effect of caffeine on sprinting performance. Effectively then we optimise their ability to sprint. So going back to our table from before I'm going to add our results now to the bottom. So we found the same result. We found exactly the same result as Anselm found. Which made me go, oh hang on a minute, what's going on here? So it's one of those bizarre circumstances where you think is there something wrong with all these studies then? And I noticed a couple of things. Most of them had used 30 second sprints. 30 second, we call them wingate sprints, cyclogometer sprints they are. And there's some evidence that in a 30 second sprint people adopt something of a pacing strategy subconsciously but they do. So I thought okay well let's address this issue then. So this is the latest study, this paper is in review at the moment. So I would just explain to you what we did. People had to do nine visits to our laboratory. We compared a 10 second sprint with a 30 second sprint. So the first thing to notice, this is just for the possible, is that the 10 second sprints were higher than the 30. We are telling these people go flat out right, as soon as we say go we want you to sprint. And somehow their brains go in. This is going to hurt and I'm just going to hold back a little bit. And yet they have no idea that they are doing that. The other thing to be aware of is if we do a standard resistance for these tests, we get a lower power output than if we optimise that resistance. It's a bit like if most people have ridden a bike at some time, if the gear was too low and you were spinning your legs around, you'd be spinning them around and not being able to generate any power output. But that's why in the real world you select a gear, don't you? You pick the best gear to optimise performance. And when we optimise it we get a higher power output. If we put our caffeine results on there, the thing we see is that, under the standard torque, you just can't spin your legs fast enough. So whether you've had caffeine or not, we're not getting any effect on performance. If you're doing a 30 second sprint, I think that the pacing issue prevents caffeine from having a real effect. And if you optimise the power output but still do 30 seconds, again pacing overrides that response. But if you take pacing out of the equation and if you optimise the resistance, then we get a significant effect. So there is an effect of caffeine in a real world situation. I've got to wrap this up pretty quickly. Caffeine, summary slide, it increases performance. Time trial performance by yet generally about 3% but it can be as high as 6%. Sprinting performance under normal conditions. Mechanisms probably related to a central effect and an effect within the muscles. And that's linked to a mechanism associated with the antagonism of adenosine receptors, which is way beyond the scope of this presentation. But there are issues in studies with sample sizes being too small and finding no effect when sometimes there is one and vice versa. Physiological effects increases heart rate during time trials but solely because you're working harder. Reduces how hard you feel you're working. And that probably explains a large part of why you're performing better and a clear increase in blood lactate. I'm going to leave you with my final slide. I'm going to finish off in the words for those of you that remember porky pig. You have to keep going. Wait for it. Wait for it. Thank you very much.