シャドーイング練習: How Caffeine Affects Exercise & Athletic Performance - 動画で英語スピーキングを学ぶ
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Caffeine is one of the most widely used psychoactive substances in the world.
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Now, most of the time we think of caffeine as a stimulant that could help us feel more alert or awake, or get us through the workday, if you will.
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However, caffeine as a performance enhancer for exercise, sports, and athletics is getting more and more attention,
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with people using energy drinks or pre -workout supplements that contain caffeine, with the hopes in that it could maybe improve endurance,
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or improve weightlifting capabilities or even just improve performance in certain sports.
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So in today's video we're gonna talk about if caffeine can actually improve exercise and athletic performance, how it could possibly do this,
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and the amount that you would need to take in order to get some of these potential benefits.
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It's going to be a stimulating one, so let's do this.
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So let's start by answering the first big question.
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Can caffeine improve exercise and athletic performance?
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Now there have been countless studies done on this, a handful of which we'll include in the description below, but the overall answer is yes, caffeine can improve exercise and athletic performance.
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And it seems that these benefits of caffeine can be applied to a wide range of different exercises.
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For example, caffeine has been shown to improve exercise capacity at prolonged submaximal exercise,
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things lasting longer than 90 minutes like a long run or a long bike ride, but it has also been shown to improve it at the mid -range or more of a little bit higher intensity,
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something that you might only be able to do for like 20 to 60 minutes.
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Not only that, it's been also shown to improve at the higher intensity, it's like that high intensity interval timeline of one to five minutes.
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So that you can see caffeine
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and these improvements can be applied to a wide range of cardiovascular dominant type exercise
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that requires a lot of output from the heart and cardiovascular system.
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Not only that, caffeine has also been shown to improve movement velocity during resistance training, so moving weights faster, and also has been shown to improve reaction time.
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So you can see how these characteristics or improvements in those two characteristics could be applied or be beneficial to weight training,
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or sports that require explosive movements like throwing or jumping, or maybe even a sport that might require improvement in reaction time,
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like maybe you're a martial artist and you need to react to a ninja kick coming towards your head.
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But how is caffeine doing this?
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What is it doing inside of your body that is accounting for these potential performance benefits?
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Well, we're going to take a look at two main mechanisms.
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One is how caffeine is a stimulant of the central nervous system, and the central nervous system or CNS in anatomy just includes the brain and the spinal cord.
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And then we'll also look at how caffeine could possibly affect muscle tissue.
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So let's start with the central nervous system by zooming in to what we'd find in your brain.
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Now to be fair, this is a very simplistic drawing of what you'd find in your brain.
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Really I just drew one neuron or one nerve cell, but the reality is you'd find billions of these neurons throughout your brain and nervous system.
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But we actually only need to take a look at one to understand how caffeine affects athletic performance.
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So if we take a look at this extension from the neuron, this is called the axon.
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And I've drawn some branches here and I've zoomed into one of those branches by drawing it up here.
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It's called the axon terminal, just the end of the axon and there are multiple receptors or chemicals that you find throughout your brain and nervous system.
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We're obviously gonna focus on the receptor that has to do with caffeine, and I've drawn this in as these little green Ys, and these green Ys represent the adenosine receptor.
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Now the blue diamond is the actual adenosine molecule which will obviously bind to the adenosine receptor, like a lock and key analogy.
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You need a very specific shaped key to fit into a very specific shaped lock in order to turn
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or activate that lock.
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Now, it's thought that adenosine will build up on the outside of your neurons as the day goes on.
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And maybe you've heard of something called ATP, which stands for adenosine triphosphate.
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ATP, or adenosine triphosphate, is the energy currency for your cells.
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And your neurons actually burn through a lot of energy or ATP throughout the day. So again,
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that adenosine starts to build up on the outside of the neurons and then can start binding to those adenosine receptors.
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But what does that cause to have happen?
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Well, when adenosine binds to the adenosine receptors, it suppresses the activity of your neurons.
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So your neurons will fire less frequently, less intensely.
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And to you, that feels like you might feel a little bit more tired or fatigued, less focused, less alert.
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But we bring caffeine into the picture.
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You ingest it in some way, it gets into your bloodstream.
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And we've got this nice little blood vessel coming into the brain here with our little red caffeine molecules
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and the caffeine will diffuse from the bloodstream and bind to one of those adenosine receptors.
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It's close enough in shape to the original adenosine to bind, but not close enough to actually activate the receptor.
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Maybe you've put a key into a lock that.. fits in there but not quite enough to actually turn the lock.
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Think of caffeine as doing that as getting in that lock, getting in that receptor and blocking it, so then adenosine can actually get into those receptors.
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So caffeine blocks the effects of adenosine and therefore has these opposing effects.
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Instead of feeling tired, less alert, more fatigued, you get increased awareness,
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increased alertness, you're more focused and you can definitely apply those characteristics to athletic performance
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and performing better in certain sports to be more focused and more alert.
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But it doesn't only just stimulate or increase awareness, caffeine also suppresses your perception of effort.
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Meaning, you're exercising at a certain intensity, it will feel a little bit less of an effort
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or you feel like you're putting less effort in than you would without caffeine.
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Now, caffeine also suppresses your perception of pain to a certain degree.
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And so if you also suppress pain to a certain degree, we've all had those moments when we've been exercising
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or playing sports where it's uncomfortable or maybe even causing a little bit of pain.
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So if caffeine can also suppress the pain a little bit, again, you're going to be able to push it a little bit further and therefore increase athletic performance. So hopefully
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that gives you a good baseline understanding on how caffeine works
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on the central nervous system to help you feel a little bit more focused and alert during sports and exercise, as well as helps to diminish that perception of effort and even pain and discomfort.
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But how does caffeine affect your muscle tissue?
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Well, there are studies that suggest that caffeine affects intramuscular calcium or the calcium inside of your muscles.
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Now this is significant because calcium plays a huge role on how your muscles contract.
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So let's quickly explain this and then apply it to caffeine.
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If you take a look at this biceps, you can see that it's made up of multiple muscle fibers or muscle cells.
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And if we zoomed into an individual muscle cell and into the myofibro, we would see that we have these little contractile subunits called sarcomeres.
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And these sarcomeres are stacked end to end to end lengthwise throughout the muscle.
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And this is about what the inside of a sarcomere would look like with our little whiteboard drawing here.
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But this is where we can figure out how calcium works.
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So taking a look at this picture of the sarcomere, you can see the thick filament in red.
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And it kind of looks like a bundle of golf clubs
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and each individual golf club would be a myosin molecule which is a contractile protein.
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Now keep in mind I will mention some of the names here, but you actually don't have to memorize all these names to understand the concepts, I'm just going to mention the names for all the anatomy and physiology nerds out there.
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But those myosin molecules
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or the myosin heads where you'd actually hit the ball with the golf club want
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so badly to bind to the thin filament which is in green
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and it looks like little circular beads slightly twisted and each little bead or circle would be an actin molecule, another protein.
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Now the problem here is that the myosin
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and the actin can't bind together yet because that blue line that's wrapping around the thin filament or those actin molecules,
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this is called the troponin tropomyosin complex or just TTC, it's blocking those binding sites.
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And this is what a muscle actually looks like at the microscopic level in the resting state.
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But, when the nerve sends the signal to the muscle to make it contract, what happens is is calcium within the muscle cell
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and therefore within the sarcomere will actually be released and binds to the TTC,
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that blue line, and shifts it slightly out of the way so now myosin and actin can bind and myosin ratchets.
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And you get this ratcheting effect throughout all those sarcomeres and that in turn would shorten the muscle and create the contraction.
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So, what does this calcium have to do with caffeine?
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Well, there are studies that suggest that caffeine can enhance
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and increase the amount of calcium released within the muscle cell and therefore within the sarcomere, thereby enhancing the contraction of the muscle.
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And this could in part explain why they were seeing increases in contraction velocity during resistance training
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when people were supplementing with caffeine.
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And you could obviously apply this to being beneficial to weight training
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and even sports or athletic events that require explosive movements like we mentioned earlier,
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throwing, jumping, sprinting, etc. Caffeine can also affect the cardiac muscle tissue within the heart, causing that cardiac muscle to contract with more force during each beat
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and therefore delivering more blood and oxygen to your skeletal muscles throughout your body.
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And you can see if you get more blood and oxygen to working skeletal muscles, there could be multiple benefits or enhancements to different types of exercises and athletic events.
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So how much caffeine do you need in order to get some of these benefits?
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Well, it used to be thought
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that you needed to take as much as 5 to 6 milligrams of caffeine per kilogram of body weight.
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So I weighed in at about 184 pounds this morning and if we converted that to kilograms, that put me at just under 84 kilograms.
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And so, if I went with a 6 milligrams of caffeine per kilogram of body weight, that'd be 6 times 84 and I'd be taking over 500 milligrams of caffeine.
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Now, I don't know about you but
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that amount of caffeine for me would be a lot and I'd likely just be bouncing off the walls.
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Now, luckily, the more recent research has shown that you need much less than that to get some of these performance benefits,
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almost half of that, like 2 to 3 milligrams of caffeine per kilogram of body weight.
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So, if I went with a three, I'd be taking about 250 milligrams.
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If I went with a lower end at two, I'd be taking in about 167 -ish milligrams of caffeine.
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Now, most of the pre -workout supplements actually have about 200 milligrams of caffeine, which is a pretty good starting point.
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But if you're one of those that's very caffeine naive, you don't take a lot of caffeine or maybe you're a little more sensitive to it,
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you could start even lower at like a one to two milligram of caffeine per kilogram of body weight
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and in these levels
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that we're talking about two to three milligrams per kilogram of body weight are all well studied
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and are relatively safe for most people but
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if you continue to push the level eventually you're just going to get to creating side effects
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and even potential safety concerns
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because caffeine does not have what we'd call a dose response
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relationship meaning the more you take the more performance benefits for exercise and athletics that you're going to get.
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You're going to get to a point where that peaks out
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and then you're just going to be dealing with side effects and again potential safety concerns.
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And another thing we need to mention is timing.
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When should you take the caffeine?
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Caffeine is rapidly absorbed with about 99 % of it making it into the bloodstream within about 45 minutes of ingestion.
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So you should take it about 30 to 60 minutes prior to exercise
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or whatever sporting or athletic event you're trying to get some of these caffeine induced benefits from.
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But what if If you're like me and you don't like to take caffeine every single day, maybe you don't drink a lot of coffee or other caffeinated beverages and personally,
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I just don't like the idea of feeling beholden to something
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that I could potentially develop a tolerance or dependence to and that can happen with caffeine.
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Anyone who's been on caffeine consistently or for an extended period of time
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and then they've cut it out cold turkey has likely noticed some of those withdrawal symptoms like headaches, irritability and other potential withdrawal symptoms.
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Now, even though I don't like taking caffeine every day, it's still extremely hard for me to ignore some of these potential performance benefits.
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So what do I do?
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I tend to selectively pick and choose
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when I'm going to take about 200 milligrams of caffeine and they're generally centered around more competitive days.
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So on my regular training days, I don't usually take any caffeine.
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But if I know I'm going to run say like an obstacle course race on a Saturday
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or maybe have a really competitive game of basketball with my friends, I'll take some caffeine 30 to 60 minutes prior to those events.
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And so for me, I'm taking it at most one to two times a week.
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And that's more of just a personal choice for me to try to kind of avoid any
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or reduce my risk of developing the dependence or tolerance to caffeine.
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But that does not mean that you can't take caffeine every day.
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Plenty of people do it.
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Plenty of people take pre -workout almost every single day, drink their coffee every single day, and that's okay, and that works for them.
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You just have to also realize that if you decide to cut back on it or cut a cold turkey, there is some of the risk to developing some of those potential withdrawal symptoms.
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So hopefully that gave you a good understanding of how caffeine can help with exercise and athletic performance.
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And I wanna leave you guys with an incredible learning opportunity.
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And that's by saying thank you to the sponsor of today's video, Brilliant.
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Brilliant .org is an amazing interactive online learning platform for STEM subjects.
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It's one of the best ways to learn math, science, and computer science.
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And trust me, I wouldn't say it's one of the best ways to learn math, science, and computer science if I didn't actually use Brilliant myself.
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I have it on my phone.
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I also use it on my laptop.
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And some of my favorite courses are the courses on scientific thinking
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because I love challenging my logic and learning how to apply new things that I've learned to actual real -world situations.
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Another incredible thing about Brilliant is that they are constantly adding new lessons each and every month.
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So no matter where you are in your educational journey, whether you're in junior high, high school, college, or just want to be a lifelong learner, Brilliant will definitely have lessons that are applicable to you.
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So if you want to become a little bit more brilliant, go to brilliant .org slash IHA to start your free 30 -day trial.
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Plus, the first 200 people will get 20 % off their annual subscription.
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We'll also include that link and the info in the description below.
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And I do want to mention that we do have another caffeine video
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that we've done previously
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that goes into a little bit more of the interactions in the central nervous system
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and talks a little bit more about the potential side effects.
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So, we'll link that to this video.
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And I also want to say thank you all so much for your support and watching all of our crazy
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anatomical and physiological videos.
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We really appreciate it and we couldn't do this without all of you.
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So, if you want to like, we definitely appreciate that.
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If you're not subscribed and you want to, go ahead
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if you feel the need and of course leave some comments below and we'll see you next time
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この動画で身につくスピーキングスキル
科学的なトピックを明確に説明するための語彙と構造、因果関係を伝える表現、そして長文を流暢に話すリズムが身につきます。「caffeine affects athletic performance」のような主張を裏付ける説明を聞き取り、自分の言葉で再現することで、論理的な話し方が向上します。
聞き取りに注意すべき発音・リンキング
動画の中では「caffeine is」が「caffeinis」のようにリンクされ、「a lot of」が「alotta」に短縮される部分があります。また、「adenosine triphosphate」のような長い単語のアクセント位置も重要で、「adéno sine triphósphate」と発音されるので、聴き取りやすいように注意しましょう。
ネイティブのように話すコツ
スピーカーは重要な用語（例えば「central nervous system」「adenosine receptor」）を強調し、説明部分はゆっくりと、結論部分ははっきりと発音しています。「So let's start by answering the first big question.」のようなフレーズのリズムを真似ることで、自然な会話の流れが作れます。shadowspeaksや英語シャドーイングのサイトで練習する際は、これらのリズムとストレスを意識的に模倣してみてください。
シャドーイングの際は、「it's thought that...」「but we bring caffeine into the picture」のような接続詞の使い方も覚えておくと、話がスムーズに繋がります。shadow speakやshadow speechの練習で、ネイティブの発音とリズムに慣れることで、自分の英語も自然になります。
この動画の文法
話し手がよく使っている文型を、動画の実際の表現とともに紹介します。
| 文型 | 動画での表現 |
|---|---|
| 条件文 if + 節, will/would + 動詞 — 条件とその結果 | if I went with a three, I'd be |
| 現在完了形 have/has + 過去分詞 — 過去の出来事が今も関係している | have been · has been shown · has also been shown |
| 受動態 be + 過去分詞 — 誰がするかより、何が起きるかに焦点を当てる | can be applied · has been shown · been shown |
| 関係詞節 who / which + 節 — 人や物について情報を加える | molecule which will · molecule which is · filament which is |
シャドーイングとは？英語上達に効果的な理由
シャドーイング（Shadowing）は、もともとプロの通訳者養成プログラムで開発された言語学習法で、多言語習得者として知られるDr. Alexander Arguelles によって広く普及されました。方法はシンプルですが非常に効果的：ネイティブスピーカーの英語を聞きながら、1〜2秒の遅延で声に出してすぐに繰り返す——まるで「影（shadow）」のように話者を追いかけます。文法ドリルや受動的なリスニングと異なり、シャドーイングは脳と口の筋肉が同時にリアルタイムで英語を処理・再現することを強制します。研究により、発音精度、抑揚、リズム、連音、リスニング力、そして会話の流暢さが大幅に向上することが確認されています。IELTSスピーキング対策や自然な英語コミュニケーションを目指す方に特におすすめです。