Lesson video

Hi there.

Welcome to today's lesson.

My name's Mr. Swaithes and I'm really looking forward to working with you today.

So, today's lesson is called EPOC and the recovery process.

It comes from the unit anatomy and physiology, aerobic and anaerobic exercise.

And I wonder, have you ever heard of that term EPOC before? Perhaps not.

So, EPOC is short for, excessive post-exercise oxygen consumption.

I'll say that again.

Excessive post-exercise oxygen consumption.

So, it's basically all about the fact that, after you finish exercise, you keep breathing at an increased rate for a little while.

And why do you think that is? Well, by the end of today's lesson, you're gonna be able to explain when lactic acid accumulates and why it accumulates.

What EPOC is and how to optimise recovery, after vigorous exercise.

The key words for today's lesson are lactic acid, oxygen debt, EPOC or excess-post exercise oxygen consumption and recovery.

You might want to pause the video now to make a note of those keywords and their definitions, but we'll definitely be revisiting them during the lesson.

So, we have split up today's lesson into three parts.

First of all, we'll be looking into lactic acid and why it accumulates.

Then we'll have a look at that EPOC and the process of excess post-exercise oxygen consumption.

And then we're gonna evaluate some of the strategies that help promote recovery.

I hope you're ready.

Let's get going.

So, Sam's here and Sam's wondering what is lactic acid and what causes it to accumulate in the body? Any ideas? That's right.

Lactic acid accumulates during anaerobic exercise, so anaerobic exercise.

And that's when the intensity of exercise is higher than the body can manage to provide sufficient oxygen to enable the complete breakdown of glycogen.

And we know don't we, that glycogen is a long chain of glucose molecules and glucose is basically sugar, isn't it? So, that comes largely from carbohydrates in our diet.

So, we eat carbohydrates, they then get stored in the body as glycogen.

And a better way to store them is long chains of glucose molecules called glycogen.

And that's what can get circulated around to your muscles to get combined with oxygen to produce energy for exercise.

But if we're exercising at a really high intensity, we don't provide enough oxygen for that complete breakdown of glycogen.

And instead partial breakdown happens which causes this byproduct called lactic acid, which will accumulate in our muscles, perhaps if we're sprinting for example.

Okay, so during intense exercise, our muscles require energy faster than oxygen can be delivered by the blood.

And there we've got a picture, haven't we? Of the the blood vessels and those red blood cells circulating around the body, carrying oxygen.

So, fortunately anaerobic respiration provides this energy quickly, but it comes at a cost.

And let me give you an example.

If I was sat here recording this lesson and suddenly a saber-tooth tiger appeared at my window, I would have what we call the fight or flight response, I would have this adrenaline release and I'd be able to sprint away from that saber-tooth tiger really quickly.

And I would only be able to sprint briefly, but hopefully it would get me to safety and evolutionary, that's how the body's been designed to be able to cope with that need for immediate exercise.

Because what we can't do is go, "Oh, I've seen a saber-tooth tiger.

"I better increase my breathing rate, "increase my heart rate, "start sending more blood to my leg muscles "and then jog away from it at a pace "that I can keep supplying sufficient oxygen "to keep going for a long period of time." So, that's why that anaerobic energy system is so important.

But as I said, it causes the incomplete breakdown of glucose and when incomplete breakdown of glucose happens, lactic acid forms in the muscles and then it spills out into the bloodstream and that lactic acid causes a drop in your pH.

And you might have experienced like a burning sensation in your muscles.

Maybe you've done a 400 metre sprint at school, around the track and you've felt that burning feeling in your legs and almost a temporary fatigue, you've had to slow down or stop.

Well, that's due to that pH and that's because of lactic acid buildup.

Let's do a quick check.

True or false? Lactic acid builds up during low intensity exercise.

What do you think? That's right, that's false isn't it? And can you tell me why.

Yeah, so lactic acid is a byproduct of anaerobic respiration and the incomplete breakdown of glycogen.

And as I said, glycogen is that long chain of glucose molecules that primarily comes from the carbohydrates that we eat in our diet.

Whereas lactic acid does not accumulate in low intensity exercise.

So for example, walking or jogging at a steady pace and the fitter you are, the faster you can actually jog, without building up lactic acid.

So, that's one of the benefits of training.

So, if lactic acid accumulates in your working muscles and it builds up to a point where it then needs to spill out into the bloodstream, and as I've said, depending on your level of fitness and hence your resistance to fatigue or ability to cope with that lactic acid, you either forced to slow down or stop.

And perhaps if you're a super endurance trained athlete, you don't need to stop at the same intensity that perhaps I would.

So, if I went out to do a marathon run with an endurance trained athlete, there would be able to run at a faster pace than I could cope with and I would build up that lactic acid and need to slow down or stop whereas they could keep going.

So, when exercise intensity decreases, so in that case of me running with that marathon runner and I've stopped or maybe I just slowed down a bit, and by doing that sufficient oxygen is then supplied again to the working muscles and they can metabolise that lactic acid away, they can turn it into energy and clear it from the body.

So, that's why once you've had a bit of a breather, I guess, you can then go fast again, you can work anaerobically again.

It's true or false then, lactic acid is harmful and we should avoid letting it accumulate at all costs.

What do you think? <v ->That's right, that's false.

</v> And can you tell me why.

Okay, so lactic acid is a natural part of that anaerobic respiration, that kind of fight or flight response, that ability to do intense exercise, powerful, explosive contractions.

And it's not harmful in moderation.

In fact, it's needed for that to happen.

And it's a great backup system that enables your muscles to keep working when oxygen supplies are limited.

And maybe you've played a football game or a netball game where there's periods of the game where you are jogging around, but then when you sprint, perhaps you sprint into score a trial to counter attack after getting hold of the ball.

And when you do that, you'll likely be building up lactic acid and you can do that for a while, perhaps up to 60 seconds.

And then you need to slow down again in order to get rid of that excess lactic acid.

So, that brings us nicely into the first practise task for today's lesson.

So, here's Erin and she likes doing hill sprints.

So, she runs up this hill for 20 seconds and then walks back to the starting point, before repeating it again.

And she does that 10 times.

So, 10 sets of 22nd hill sprints.

And I'm wondering, can you describe what lactic acid is? And then can you explain why tactic acid accumulates in these hill sprints that Erin is doing? Pause the video now and come back to me when you are ready.

Let's see what you came up with then.

So for question one, where we wanted you to describe what lactic acid is, hopefully you put something along the lines of lactic acid is a byproduct of anaerobic respiration and it accumulates in the muscles during intense exercise and that contributes to muscle fatigue and soreness.

And then on into the second part of the question then where I wanted you to explain lactic acid accumulation and why it happens.

Hopefully you said that as Erin's sprint uphill, her leg muscles will be demanding more oxygen than her cardiovascular and respiratory systems can provide.

And as a consequence of that, she will build up lactic acid.

But then as she walks back down again, some of that lactic acid will be removed, because she continues to breathe at an increased rate and her heart keeps pumping really fast.

So, excess oxygen is delivered to the muscles, during that recovery of walking back down.

And that's what enables her to then go and sprint again.

And if she trains regularly, she'll perhaps be able to do more than 10 sets in the future.

Maybe she can do 12 or maybe she can sprint uphill for 30 seconds, instead of 20 seconds.

So, you remember some of that around progressive overload of training.

Well, that brings us nicely into the second part of today's lesson then where we're gonna outline that process of EPOC.

And can you remember what EPOC stands for? Well, Sam's here and Sam's wondering why do I keep breathing heavily after hard exercise, like sprinting up a hill.

So, let's think back to Erin.

She sprinted up the hill for 20 seconds and then she stopped.

Why is she so outta breath at the end of the sprint as well as during it? And in fact, sometimes you're more outta breath afterwards than during.

Well, Andeep is wondering, why does his coach encourage him to keep moving and do an active cool down after training sessions? Any ideas? Well, when we start to exercise, but also during intense periods of exercise, we build up what's called an oxygen debt.

So, this is when insufficient oxygen is being delivered to provide all the energy for exercise, i.

e, lactic acid is building up in those muscles, because of that oxygen debt.

So, as a consequence of that, we stop exercising and we consume additional oxygen to repay that debt and to convert lactic acid to glucose and carbon dioxide and water, i.

e, that formula for aerobic respiration, isn't it? We're turning it into glucose and then it's carbon dioxide and water.

So, this is called excess post-exercise oxygen consumption or EPOC for short.

And it's a really important part of recovery.

So, here we've got the oxygen debt and EPOC curve and what this is shown in the dark colour is the oxygen consumption during exercise.

And you can see towards the left hand side there in that kind of teal colour, actually because it takes a little while for our breathing rate to increase and our heart rate to increase as we start to exercise, doing a submaximal activity such as a gentle jog that this curve is showing.

Takes a little while for that breathing rate and heart rate to get up to a level where our body is providing the amount of oxygen it needs to keep running at that rate and working aerobically.

So, what we've got is during this period of exercise we've got steady state oxygen, sorry, steady state exercise where the oxygen supply meets the demand.

However, as I've just mentioned at the left hand side of this curve we can see the teal area and we refer to that as the oxygen debt.

So, this is the period in which we are doing exercise that requires more oxygen than our body is currently providing because we haven't quite built up that higher breathing rate and heart rate and circulation of oxygen to provide that necessary oxygen to the muscles.

So, we build up this amount of oxygen debt and it's due to this oxygen debt that after exercise, we keep breathing and our heart rate remains elevated.

That above kind of natural resting levels, because of what we can see here, this EPOC, the excessive post-exercise oxygen consumption.

And actually this purple area here, the area under that curve, would be equal to the teal area on the left.

So, the bigger the oxygen debt before or even in some instances during exercise, if it's maximal exercise, the bigger the EPOC after exercise.

So, I guess the rule of thumb for that is if you don't do a thorough warmup, you start exercise or you have quite a significant oxygen debt prior to exercise, you'll want to keep a gentle jog after exercise and keep breathing and heart rate elevated for a little bit longer afterwards to clear that oxygen debt out of your system.

Let's do a quick check then.

So, what does EPOC stand for? Is it excessive post-exercise oxygen carrying? Is it B, excess post exercise oxygen consumption? Or is it C enhanced postoperative care? What do you think? Well done? It's B isn't it? So, it's all about that extra consumption of oxygen, after exercise and by maintaining that elevated cardiovascular, so heart rate and stroke volume, but also that elevated respiratory rate.

So, breathing rate and breathing depth during recovery that oxygen debt can be repaid.

And actually that term oxygen debt is a little bit outdated now, we tend to use the term EPOC instead and sometimes even refer to something, called an oxygen deficit.

So, like a lack of oxygen early on in exercise that is repaid through that EPOC.

So, that's why after strenuous exercise, so if we go back to that example earlier of sprinting up a hill and being really outta breath afterwards, well we're really outta breath afterwards, because we need to repaid that oxygen debt.

So, we maintain an increased breathing rate, an increased depth of breathing, an increased heart rate, an increased stroke volume.

And obviously those two combined, make an increased cardiac output and then also an increased blood flow to the working muscles.

So, vasodilation of those arteries and arterials that are feeding blood to our working muscles.

So, in the instance of running, it'd be feeding lots of extra blood to the leg muscles.

Sam's back again, "What happens if you stop and sit down, "immediately after strenuous exercise?" So, let's think of an example of perhaps you've done a 400 metre run or sprint at school and as you cross that finish line, the temptation's there, isn't it? To sit straight down, 'cause you're exhausted.

Well that's not the best thing to do, is it? And I'm sure your PE teachers have told you to keep moving, to stand up tall, perhaps get your hands on your head and keep taking deep breaths and walking around.

Well the problem if you just collapse on the finish line is that blood pools in the legs and hence fresh oxygen supplies are not as easily pumped around the body or delivered to those muscles.

So, the lactic stays there, the fatigue lasts for longer.

So as a consequence, as I said, that lactic acid is not removed and that's why you're encouraged to do that active cool down to get up and to get moving.

Here's another check then.

So, a gentle jog after exercise helps with EPOC.

Is that true or false? That's right, it's true.

And can you tell me why? Yeah, so jogging will keep your breathing and heart rate elevated and that flushes fresh oxygen around the body as a faster rate than if you just stop exercising completely.

And hence that improves your recovery.

So, you should always do that gentle jog after exercise, particularly if it's intense exercise to help with recovery.

That brings us nicely to the second task for this lesson.

So, if Charlie was running a thousand metres, could you draw and label a graph to represent oxygen consumption during an after the race? Ensure you label the following features on your graph, oxygen debt, EPOC, exercise and recovery.

And then secondly, I'd like you to think about why her breathing rate, remains elevated after the race and capture that.

Pause the video now whilst you have a go at that and come back to me when you are ready.

Okay, so does your graph look a little bit like this? So, here we can see the oxygen jet on my diagram is that teal colour at the beginning of the 1000 metre run.

Then we've got the oxygen consumption during it and then afterwards as recovery starts, we've got that EPOC curve of recovery.

And then secondly, were you able to justify why her breathing rate remained elevated? Well hopefully you said something along the lines of, Charlie's breathing rate remains elevated after the race in order to repay oxygen debt and that oxygen debt was created due to anaerobic exercise at the beginning of the race.

It also helps to remove lactic acid, during the recovery process.

Into the third part of today's lesson where I want to evaluate the strategies that promote recovery.

So, we've said that an active cool down is really important, but what else could you do after exercise to help get the body back to its pre-exercise state? Well, Sam's wondering what is the best way to recover from exercise to be able to train again or to compete again soon? Well, we've said, haven't we? An active cool down keep moving, keeps that heart and breathing rate elevated and that helps remove lactic acid.

And a gentle jog followed by some stretches is a great idea to do that.

But what else do you think might help this? If you think of elite athletes, what have you seen them perhaps doing, after a big match to help recover faster? Before we look at those answers, let's just remind ourselves, which of the following is achieved via an active cool down? Is it A, faster reduction in heart rate to resting levels? Is it B, a maintained elevation of heart rate or is it C, maintained elevation of breathing rate? What do you think? Which of these and it might be more than one, is achieved via an active cool down.

That's right, B and C, isn't it? So, your heart rate and your breathing rate are maintained high.

So, it actually slows down that heart rate return to resting levels.

But that's a real positive thing, 'cause it helps clear out that lactic acid and get energy replenished in your muscles.

But we can also do some other things during recovery to help speed up and improve recovery.

And diet manipulation is just one of those.

So, eating a high carb meal after exercise, helps replenish those energy stool.

So, you may even have heard of this idea of the first meal after exercise is almost free.

You can take on lots of carbohydrates after exercise, without putting on weight.

So, it's a really nice strategy if like me, you like eating and you also like exercising, so you can really enjoy a good meal after exercising.

Sports drinks perhaps are another source of that energy replenishment and proteins also help with growth and repair of muscles.

So, these three strategies, proteins obviously coming from lean meats and if you've done some really intense exercise you will have had little micro tears in your muscles and in order for them to recover, taking on proteins is a great way.

That's why you see a lot of protein shakes now.

So, a high protein diet is especially beneficial if you're doing strength training.

Whereas carbohydrates are needed more for endurance training recovery.

Rehydration is another key one.

So, drinking water and that replaces the fluid that's lost during exercise.

So, fluid was lost through sweating, wasn't it? So, and because of that significant water loss, you need to replenish it after exercise.

And actually we often start replacing it, during exercise as well.

We take water on board during exercise, but also we know that when we sweat we lose essential salt and electrolytes as well.

So, tension isotonic drink, might be a better way to quickly absorb that water, salt and electrolytes back into the bloodstream.

And that's basically a drink with a little bit of sugar and a little bit of salt in it, as well as the water concentrate.

Ice baths then are another increasingly popular way to recover after exercise.

And actually what happens with an ice bath and why it speeds up recovery is it reduces inflammation.

So, when you get in cold water, your extremities, your hands and your legs, your arms, will vasoconstriction the arterials that are feeding blood there, will vasoconstrict to stop blood flow from going to the extremities to help keep your core body temperature warm.

And in doing so, they reduce that inflammation, they sort of suck back out of those areas, the excess fluids.

And because of that it helps reduce muscle soreness, but it also helps improve circulation and that removal of waste.

So, in and out of hot and cold is quite a good idea after exercise.

So, particularly beneficial in high-intensity or endurance activities.

And it helps reduce what we called DOMS. So, DOMS is the delayed onset of muscle soreness and that's that achy muscle feeling that you might have 24 to 72 hours after exercise.

And then also massage, so deep tissue massage is another way to speed up recovery, 'cause we can work the muscles, increasing the blood flow to them, removing the waste products, but also relaxing those muscle fibres and reducing muscle stiffness.

We can take some of those knots outta the muscles and reducing inflammation and swelling.

So, often people will combine ice bathing and massaging as part of that recovery process in the kind of day or two, following intensive exercise.

Let's do another quick check then.

So, which of the following strategies improves recovery from strenuous exercise? Is it A, an active cool down? B, a carbohydrate rich meal? C, dehydration or D, an ice bath? What do you think? That's right, it's A, B and D isn't it? All three of those are effective strategies to improve recovery.

And of course we don't want to be dehydrated, we want to rehydrate during recovery.

So, Sam's back again and saying, what do I have to do if I'm asked to evaluate a strategy to promote recovery? Well, to evaluate, we have to judge from the available evidence.

So, the judgement will include positives and negatives of the strategy.

Well, we've not yet looked at some of the negatives to those recovery strategies, have we? So, let's just have a quick look at some of those negatives.

Well, diet manipulation, sometimes it's hard to find time to eat, after intense exercise.

And actually some of my friends, perhaps after we've played a squash match, they don't like to eat a meal after exercise.

They feel like they're not hungry.

So, that's one of the drawbacks is you almost have to force feed yourself for some people to get that energy back in.

What about hydration? Well, fluids are absorbed by the body better if they contain some salt and sugar.

So, perhaps rather than drinking water, which is hard to take on board.

And again, sometimes we just don't want to take on board all of that water.

Perhaps isotonic drinks might help.

Ice baths, well one of the negatives to these is they're not always available, are they? And they can cause a little bit of nerve damage and also feel uncomfortable.

I dunno about you, but I really don't like that freezing, cold sensation.

And then what about massage? Well, it can be very expensive and it involves physical touch obviously by whoever's doing that massage.

And for some people they struggle a bit with that.

They don't like that.

Massage guns are perhaps a good solution to that, something that you can do yourself.

And they're all about that active cool down.

Well, it takes time, doesn't it? And a commitment.

So, sometimes people skip it, they're too desperate to get off and do something else.

So, now we've worked through some of those negatives of recovery.

I wonder, can you complete task C? So, thinking back to Erin again, following her hill sprinting session, she wants to go straight home and lie down.

Well, can you firstly identify and describe four strategies that would support better recovery than just going and lying down? And then secondly, can you evaluate the use of an ice bath to promote recovery for Erin? So, this is an extended question using the command evaluate.

To have a quick reminder of how to evaluate, well, you need to share what you know, then you need to apply it and then you need to say why.

So, you're going to give a brief description of an ice bath.

You're then gonna apply that by saying how hills sprints are going to make Erin feel.

And then you're gonna give the say, so the judgement on an ice bath, what are the positives and the negatives to an ice bath? And maybe is there an alternative to that ice bath that could be used instead? So, pause the video now whilst you have a go at those two tasks and come back to me as soon as you are ready.

Well done.

How did you get on with that one? And so the first one was the easier part to this question, wasn't it? So, you might have said an active cool down, helps maintain elevated breathing and heart rates and that ensures oxygen rich blood flow to the muscles to remove lactic acid.

You might have said a carbohydrate rich diet, helps replenish those energy stores in the muscles.

So, replenish the glycogen stores.

You might have said drinking lots of water helps rehydrate and replace fluids lost during sweating.

And maybe you combine those two answers to talk about isotonic drinks that are part carbohydrate, part liquid, I guess, part fluid replacement.

And then fourthly, you might have said an ice bath helps prevent delayed onset of muscle soreness or DOMS and the last choice.

And obviously you would've only done four of these five ideas, but a massage can also help prevent DOMS. Which of those four did you get down? And then into the second part of this question then, where I asked you to evaluate an ice bath? Well, in terms of what you know, well, an ice bath involves submerging in very cold and icy water for five to 10 minutes, after vigorous exercise.

The blood vessels will vasoconstrict and that restricts blood flow.

We then need to apply, don't we? So, Erin will have used lots of anaerobic respiration, during her hill sprints, which will lead to increased levels of lactic acid in the muscles and in the blood.

So, it's highly likely she will experience EPOC, that excessive post-exercise oxygen consumption and may feel some inflammation in her knee joints from the uphill terrain.

Well, now we need to say, why don't we? So, an ice bath is beneficial to Erin as it will lead to quicker removal of lactic acid, therefore it reduces the likelihood of experiencing DOMS or delayed onset of muscle soreness.

So, the ice can reduce swelling and that leads to less inflammation in the knees.

We said, didn't we? That sprinted up puts quite a lot of strain on the knee joints.

However, so this is the negative aspect, an ice bath can feel very uncomfortable and the extreme temperature can lead to potential nerve damage.

So, we have to be really careful with it.

And I guess acclimatise ourselves to those ice bath conditions.

Ice baths are not the easy to access solution for everybody and hence Erin may feel the same benefits for an active cool down or maybe you think she would benefit from massage.

So, there we go.

We've evaluated that question.

So, it just leaves me a couple of moments to summarise today's lesson.

Lots in there wasn't there and you certainly started the lesson, I'm sure not even knowing what EPOC was.

And it's all connected to this lactic acid.

So, that fatiguing byproduct that's produced when you exercise and aerobically.

And that EPOC or excess post-oxygen consumption is required to repay that oxygen debt from vigorous exercise.

And performers must maintain elevated breathing rates, after exercise to repay that oxygen debt.

And then we looked at, didn't we? Some of the other strategies that help with recovering, we said an active cool down, manipulating your diet to take on more carbohydrate and more proteins, but also an ice bath or a massage can help prevent DOMS. So, that delayed onset of muscle soreness in the 24 to 72 hours after exercise and hence speed up recovery so you're ready to train again or compete again soon.

And a lot of this is a reminder of why we quite often in training programmes, we train hard one day and then have a rest day the next day.

Or maybe you train your upper body hard one day and then the next day you train your lower body to give the upper body that chance to recovery.

I hope you've enjoyed today's lesson and I really look forward to seeing you again soon.