Lesson video

Hi there.

Welcome to today's lesson.

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

So today's lesson is called lactic acid and recovering from exercise.

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

And in this lesson I really want to help explore with you what happens after, well in fact during, really intense exercise that causes that shaky legs feeling or shaky arms feeling if you're perhaps doing some powerful or explosive contractions with your arms. And then what we do about that after exercise.

So by the end of today's lesson, you're gonna be able to explain when lactic acid accumulates, how the body responds to different types of exercise and how to optimise recovery.

Have you ever wondered why sometimes you get that really shaky leg feeling or shaky arm feeling depending on the way you are lifting weights or perhaps where you are really working intensely, which parts of your body you're working so intensely? And why that is, and then what you can do about it.

And perhaps even wondered, you know, what would training do to that response? The key words for today's lesson are lactic acid, which is that byproduct of anaerobic respiration and it accumulates in the muscles during intense exercise.

We've also got oxygen depth, so that's the amount of extra oxygen required to remove lactic acid and replace the body's reserves of oxygen.

So that's lactate accumulation is the next one.

So that's the point at which intensity of exercise triggers a buildup of tactic acid in the muscles and in the blood due to working anaerobically, i.

e.

with insufficient oxygen.

And then finally we'll be looking at recovery and that's that time required to repair the damage to the body caused by training or competition.

And there are various things that we can do during recovery to help optimise recovery to be ready to train or to compete again.

The lesson's been broken up into two parts.

The first part will be explaining why lactic acid accumulates in the first place.

And then the second part will be describing how to maximise that recovery from exercise.

So how to recover better from exercise.

What things do you think you could do to recover better after exercise? Or maybe what things do you do? I hope you ready? Let's get going.

So Sam's got a question for us to kick it off and Sam's wondering, "What is lactic acid and what causes it to accumulate in the body?" Have you got any ideas? That's right, so lactic acid accumulates during anaerobic exercise.

So that's exercise where there's insufficient oxygen supplied to provide the energy for the complete breakdown of glucose in your muscle site.

So if that intensity of exercise is higher than the body can manage to provide sufficient oxygen to be able to work aerobically, it causes that incomplete breakdown of glycogen.

Whereas aerobic exercise, we can completely break down glycogen and there's no byproduct.

So there's no lactic acid that's produced in that instance.

So during intense exercise then, our muscles require energy far faster than oxygen can be delivered by your blood.

So you're breathing and your heart's beating and you're pumping oxygen to the muscles, but you're not providing enough for them to be able to work aerobically.

Well, fortunately, anaerobic respiration can kick in and provide this energy quickly, but it comes at a cost, and actually it's almost like an evolutionary thing that we've been able to have, this anaerobic response.

And sometimes you might refer to it as the fight or flight response.

So if a sabre tooth tiger ran at you, you would need to be able to respond immediately and explosively to get away from danger.

And if we had to wait until you'd started to increase your breathing rate and increase your heart rate in order to be able to provide oxygen to your muscles to jog away from that tiger, it might be too late.

And that's why the body's got this ability to respond immediately and far more explosively.

So much stronger muscular contractions.

But unfortunately it comes at a cost.

And actually it's that incomplete breakdown of the glucose.

So glucose is actually joined together in long chains that are called glycogen.

So you may come across the term glycogen or the term glucose and this basically comes from carbohydrates that we eat in our diet.

So those glycogen or glucose or carbohydrates from our diet are broken down and that releases the energy to cause muscular contractions.

But if you can't fully break it down because you've not got oxygen present, lactic acid builds up and that formation of lactic acid starts in the muscles and then it spills out into the bloodstream.

And once that lactate accumulation level reaches a certain threshold, you'll feel this kind of burning sensation in your muscles and it causes this temporary fatigue.

So basically you can only sprint for a short period of time.

Let's do a quick check because there was quite a lot of information there.

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

Is that true or false? That's right, it's false, isn't it? And can you tell me why? Yeah, so lactic acid is a byproduct of anaerobic respiration.

And so when there's that incomplete breakdown of glycogen or glucose, whereas lactic acid does not accumulate in low intensity exercise.

So if I go for a walk or even a gentle jog, I'll be working aerobically and no lactic acid will build up.

So if lactic acid is accumulating in the working muscles first and then it spills out into the bloodstream, well depending on your level of fitness and hence your resistance to fatigue, your ability to cope with that tactic acid in your bloodstream, you can either keep going for a little bit longer.

So elite in, you know, endurance trained athletes can actually work at quite a high threshold and build up quite a bit of lactic acid, but then metabolise it away.

So you know, there's people that can run a marathon and every a hundred metres of their marathon are faster than I could run a hundred metres.

So they're able to cope with these levels of lactic acid in their blood because they've trained to cope, to be resistant to fatigue.

Whereas for most of us, we are forced to slow down or even stop excising.

And in fact, if those elite endurance trained athletes try to run a little bit faster, they would also cross that threshold, build up too much lactic acid, and it would cause this fatigue in them to need to slow down or stop.

And that's why sometimes we refer to that idea of hitting the wall in endurance events, if you just train in that little bit too fast.

Or maybe you know you're out for a jog and then you start to go up a hill and obviously the intensity increases.

So that will cause an increase in that lactic acid accumulation.

So when exercise intensity decreases again, or maybe stop, so you stop running up that hill, sufficient oxygen is supplied again, and that enables the lactic acid to get metabolised away.

So it's not like lactic acid is super bad forever, it just causes that temporary fatigue.

And then once we can provide enough oxygen to that lactic acid, again, a whole load of chemical reactions happen that metabolise or clear that lactic acid away from the body again and actually turn it back into energy to work at low intensity.

So let's do another check.

True or false? Lactic acid is harmful and we should avoid letting it accumulate at all costs.

That's right, that's false, isn't it? And can you tell me why? Can you remember? Yeah, because lactic acid is a natural part of anaerobic respiration and it's not harmful in moderation.

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

So like I said, that immediate response if the sabre tooth tiger runs after you, or if perhaps you're out for a run and you end up needing to go up a hill and that going up the hill, you're either gonna have to slow down significantly, well, maybe if it's a short hill, you could keep at that same pace and you would perhaps start to work anaerobically, you'd build up some lactic acid and then as the slope or the incline reduces again, you can then metabolise that lactic acid away and keep going.

Which brings us nicely into this practise task, doesn't it? So Erin likes doing hill sprints.

She runs up a hill for 20 seconds and then walks back down again before repeating that 10, sorry, that 20 second sprint up.

And she does that 10 times over.

What I'd like you to do is explain what lactic acid is and why it accumulates during this sort of exercise.

So pause the video now whilst you do that and come back to me when you are ready.

Okay, what did you come up with then? So you might have said, lactic acid is a byproduct of anaerobic respiration and that it accumulates in muscles during intense exercise and that contributes to muscle fatigue and soreness.

So as Erin sprints uphill, her leg muscles will be demanding more oxygen than the cardio respiratory system can provide.

And as a consequence, she's gonna build up lactic acid, isn't she? As she walks back down again, some of that lactic acid will be removed whilst excess oxygen is delivered to the muscles during recovery.

And so she'll get rid of most of that lactic acid during her walk back down to the start line.

But then as she does another set, it will build up again.

And actually that lactic accumulation the second time will probably be slightly greater than the first time 'cause she's still got a little bit in her system from the first hill sprint.

And that's why actually she probably couldn't do more than 10 sets.

But if she trains regularly, maybe a later training session, she'd be able to do 12 sets and then 15 sets as the body responds to that progressive overload.

That brings us nicely into the second part of today's lesson where we're gonna look at how to maximise recovery from exercise.

So if you've worked really hard, how do you speed up the body's recovery? Well, Sam's back again, and Sam says, "Why do I keep breathing heavily after hard exercise like sprinting up a hill?" Have you ever experienced that? And you think, "Well, I'm not running anymore, why do I still need to keep breathing heavily?" Why do you think that is? Well, meanwhile, Andeep saying, "Well why does my coach encourage me to keep moving and to do an active cool down after training sessions?" And especially if they're kind of sprint or powerful explosive training sessions.

What do you think? Well, that's right, when we start to exercise, but also during intense periods of exercise, we build up what's called an oxygen debt.

There's that word we introduced at the beginning.

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

And therefore lactic acid starts to build up.

And this is why if you set out for a run, it'll be a little bit uncomfortable to start off with and then it's your heart rate, your breathing rate, and your body adapts to redistribute more blood to the, well the legs in this case if you've gone out for a run, you get to be able to cope with that and actually that oxygen debt starts to get reduced during exercise if it's sub maximal.

But if it was maximal exercise, i.

e, you were running really fast or you've run on for a really long time, we need to at some point stop exercising and consume extra or additional oxygen to repay that oxygen debt.

That bit at the beginning of running where we weren't providing enough oxygen for the exercise that we were doing, or maybe we've been running at a high intensity, so therefore we've been building up a bit of lactic acid.

So there's some oxygen debt there as well.

And that's the point in doing a recovery.

So a quick check then.

What is oxygen debt? Is it A, extra oxygen available during exercise? Is it B, a shortfall in oxygen during high intensity exercise? Or is it C, a lack of oxygen available during recovery? What do you think? That's right, it's B, isn't it? So oxygen debt is that shortfall in oxygen during high intensity exercise.

And it's also what happens at the very beginning of exercise before our bodies responded and got us up to a higher heart rate.

And in fact it's why just before exercise, you get that anticipatory rise, butterflies that increase in heart rate and its adrenaline release trying to help reduce this oxygen debt as much as possible.

So by maintaining elevated cardio respiratory rates during recovery, the oxygen debt can be repaid.

So this is why after strenuous exercise, you maintain increased breathing rate, increased depth of breathing, increased heart rate, increased stroke volume, and increased blood flow to your working muscles.

So we know that's called vasodilation, don't we? So we've got vasodilated arteries leading to our working muscles, perhaps your legs if you are running.

And all of that combined after exercise means that we can work really hard to flush out that lactic acid from our muscles.

So Sam says, "What happens if you stop and sit down immediately after strenuous exercise?" Have you ever done that? You've perhaps done a 400 metre sprint at school and at the end of it you've collapsed on the finish line and sat down.

Well, what happens then? Well, blood pools in the legs and fresh oxygen supplies are not as easily pumped around the body.

And as a consequence of that, the lactic acid is not removed as quickly from your legs.

So that's why an active cool down is encouraged.

So I dunno if your PE teacher has ever said to you after that 400 metre sprint, "Don't collapse on the floor, stay up tall, keep moving around." Perhaps get your hands on your head, take in deep breaths so that you're getting lots of fresh oxygen into the body and you're getting it circulated still around to where that lactic acid is, where that oxygen debt has happened.

True or false? A gentle jog after exercise helps with recovery.

That's right, it's true, isn't it? And can you tell me why? Well, by jogging you'll keep your breathing and your heart rate elevated and that flushes fresh oxygen around the body at a faster rate than if you stop exercising completely.

And hence it improves recovery.

Well, Sam's back, "What is the best way then to recover from exercise to be able to train or compete again soon?" Well, an active cool down keeps that heart and breathing rate elevated and that helps remove lactic acid.

So gentle jog followed by some stretches is a great idea.

But what else do you think might help? So as well as an active cool down, what else might help speed up recovery or improve recovery? What do you think? Well, before we find out, let's do another quick check.

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, prolonged elevation of heart rate? Or is it C, prolonged elevation of breathing rate? And maybe more than one of these is correct? That's right, B and C are correct, aren't they? So your heart rate remains elevated and so does your breathing rate.

So it takes longer to get those back to your resting levels.

But as a consequence, you've cleared that lactic acid out of the body, you've flushed it out with some fresh oxygen.

Well, the following strategies also help with recovery.

We've got diet manipulation, so eating a high carbohydrate meal after exercise helps replenish energy stores.

I'm sure you've come across lots of sports drinks that claim, and actually they are quite good at replenishing those energy stores.

We've got protein, so for example, protein shakes, but also high protein meals are required after particularly explosive contractions where you're gonna have really got micro tears in your muscles and proteins help with that growth and repair of your muscles.

And then also super important during recovery is rehydration.

So drinking lots of water and that will replace the fluids lost through sweating.

And that's quite often why sports drinks, particularly isotonic sports drinks, are really good because they not only contend the water, so the fluid, but they also have got the salts and some glucose, some sugars in that drink.

So it can do all of those things.

It can rehydrate and replace some of the energy and some of the salts lost through sweating.

And then we've also got ice baths and massage.

So these are increasingly used actually, particularly in elite sport, to reduce that inflammation at your muscles and help prevent muscle soreness the next day.

And we call that muscle soreness the next day DOMS, so the delayed onset of muscle soreness.

And ice baths and massages are a great way to reduce that.

So a quick check, which of the following strategies improves recovery from strenuous exercise? Is it A, an active cool down? Is it B, a carbohydrate rich meal? Is it C, dehydration? Or is it D, an ice bath? And again, more than one of these answers is correct.

Okay, I hope you got those three.

And of course it's rehydration, not dehydration that you're trying to do during recovery as well.

So that brings us nicely into the second and final task of today's lesson.

So let's think back to Erin during task A who was doing those hill sprints.

Well following her 10 sets of hill sprints, Erin is keen to go straight home and lie down.

Well, can you identify and describe four strategies that would be much better things for Erin to do to help support her recovery? So pause the video now whilst you do that and come back to me when you are ready.

Okay, what have you come up with then? So you might have said, an active cool down helps maintain elevated breathing and heart rates, which ensures oxygen rich blood flow to the muscles to remove that lactic acid.

So that's the most important one.

The active cool down is essential.

You may also have said a carbohydrate rich diet or meal helps replenish energy stores.

I hope you've also remembered that drinking lots of water helps rehydrate and replace the fluids lost during sweating.

And maybe you combine those two answers to say that perhaps sports drinks, isotonic drinks might be a good thing to take on board.

And then we've got ice baths, haven't we? And they help prevent that delayed onset of muscle soreness or DOMS, and we've got massages as well, which also help prevent that muscle soreness.

So that just leaves me a little bit of time to summarise today's lesson.

So lactic acid is produced when we exercise anaerobically, so at high intensity.

Yep, so that anaerobic exercise is when the intensity is too high to provide sufficient oxygen for aerobic respiration.

So it's not like we're not breathing, we are breathing, but we're not getting enough oxygen to the working muscles to work aerobically.

So we're working anaerobically.

But that anaerobic exercise can only last a short duration because it's at such a high intensity that that lactate accumulation reaches a threshold that causes fatigue, that shaky legs feeling and a need to slow down or stop.

And then we also learned that during recovery, respiratory rates remain elevated to remove lactic acid.

And we learned that an active cool down, manipulation of diet and ice baths or massage can help speed up recovery.

I hope you've enjoyed today's lesson.

I've certainly enjoyed working with you again, and I look forward to seeing you again next time.