Lesson video

Hello and welcome to today's lesson.

My name's Mr. Sway and I'm really looking forward to teaching you today.

So today's lesson is called "Muscles of the Body and Antagonistic Pairs." It comes from the unit "Anatomy and Physiology, the Muscular Skeletal System," and it's our opportunity to really delve into the names of the different muscles in the human body.

I'm sure you'll have come across most of them already, and then what those muscles do and how they work in pairs to contract to make one movement and then relax in opposition to that.

And then the reverse happens when they alternate roles.

So by the end of today's lesson, you're gonna be able to label the major bones of the human body and describe how antagonistic muscle pairs work together to produce movement.

There's some really important keywords today, so you might want to pause the video and make a note of them, but we will be revisiting them as we go through the lesson.

So agonist or prime mover, antagonist, antagonistic pairs, tendon, and rotator cuffs are the ones that I've selected that you'll really want to get your head around today.

The lesson has been broken up into three parts.

In the first section, we will be locating and defining major muscles in the upper body.

Then we'll move into the lower body, and then finally we'll be explaining how those muscles operate as pairs.

So let's get going.

I hope you're ready.

Okay.

So the human body is absolutely covered in skeletal muscles, isn't it? And they work under our voluntary control, which means when our brain tells our muscles to contract, they contract to create movement, and when muscles contract, they shorten.

Really important key message there.

And this allows us to complete everyday tasks, but also to perform complex movements in sport.

Can you point out and name any of your muscles? Maybe pause the video for a second and see if you can name some of them before we start to reveal.

Okay, let's delve into the ones in the upper body then.

So can you think which ones I've identified here on the diagram? Well, first of all, we've got that muscle on top of the shoulder, which we know as the deltoid, don't we? Responsible for all sorts of important movement like abduction of the shoulder joint.

Then we've got the pectorals, the pecs, but remember to use its full name, the pectorals, or you might have sometimes heard of it as the pectoralis major, which is one of those pectoral muscles.

Then we have the biceps.

They're actually two biceps and they're known collectively as the biceps.

And then we've got the trapezius, that big triangular muscle across the shoulders on the back, particularly big in swimmers and perhaps rugby players.

We've got the rotator cuff, so they're identified in that the white colour in the corner there.

And really important for anyone who does lots of throwing.

Underneath that, we've got the triceps.

So lots of you will know biceps on the front of your arm, two of those triceps on the back of the arm, three of those, and those two muscle groups work together really well.

Then we've got the latissimus dorsi, the big sheet of muscle underneath running all the way up the length of the back.

So let's explore each of those muscles in a little bit more detail and consider what movements they create.

So deltoid muscle that's covered over your shoulder joints.

See if you can feel yours now as I'm talking.

And then abduct, lift your shoulder up to the side and you'll feel that deltoid muscle contracting, especially if you're holding a weight.

An example of that in a sporting scenario would be reaching out to the side to save a goal.

If a goalkeeper spots that shot right at the edge of the net, they'd reach out to the side to save it.

Can you think of any other examples of the deltoids working? Okay, let's move on to the biceps, perhaps the most widely known muscle in the human body.

So they cause flexion at the elbow joint.

And example of that, it's not actually what we see in this image, but as that rock climber now pulls their body up, it'll be flexion of the biceps muscle that's causing that elbow to bend.

The latissimus dorsi then.

So that big sheet muscle across the back, so that one pulls the arms down towards the body.

So from this position down into adduction, and a really nice example of that in action is during the pull phase of freestyle and butterfly swimming.

So two of those strokes there.

So let's do a quick check then, see what you've picked up so far.

Which of the following is responsible during the preparation phase of a chest pass in netball? So as you bring the ball in to your chest.

Is it: A, the pectorals; B, the biceps; C, the triceps; or D, the deltoids that are causing that movement? That's right.

It's B, the biceps, isn't it that cause that flexion at the elbow joint.

Okay, the trapezius then, that muscle across the top of your shoulders and working with the deltoids that causes that abduction movement out to the side.

Nice example of that in action here is this discus thrower with his arm out to the side holding the discus.

And then there's a whole group of muscles called the rotator cuff muscles, and they're in the back here and their role is really important in stabilising the shoulder joint.

So you can see they're almost placed right on top of the shoulder blade or scapula, and they allow a wide range of movement and help stabilise that joint when it's happening.

So any throwing activity that you do will require those muscles to be involved.

So the discus, the golf swing, the tennis serve, the American football quarterback as they're making their javelin pass.

and in fact, cricketers and American footballers, well, cricket bowlers and American footballers in particular have problems sometimes with their rotator cuff muscles and injuries, but you'll learn more about that in a different lesson.

Then we've got the triceps, so they contract to cause extension at the elbow joint.

An example of that would be that left arm in that extended position as the ball is thrown up for this tennis serve.

Let's look at the pectorals then.

So their job is to pull the arms back down.

If you put your arm up to the side and then lower it down, you can feel your pectorals contracting as you do that.

And an example of that would be the downward phase of a golf swing.

So is that arm sweeps down and pulls the club down.

Now let's move on to the core.

So we've got upper body, later we'll do lower body, and now we're on the core region in between.

What's your six pack called? That region of muscles at the front there? That's right, the abdominals, isn't it? Or often people refer to it as your abs, but let's make sure we use its full anatomical term.

So the abdominals and then we've got the gluteals, and again, the gluteals are made up of a number of different muscles.

So sometimes you'll hear people talk about their gluteus maximus, which is just one of those gluteal muscles.

So let's do a quick check then.

Which of the following is responsible for adduction at the shoulder? Is it: A, the pectorals; B, the biceps; C, the triceps; or D, the deltoid.

Well done.

Yes.

It's pectorals, isn't it? They pull the arm back down from up at the side.

Okay, so when your abdominals contract that causes flexion at the spine, but also at the hip joint.

An example of this would be tucking into a somersault position or a forward roll in gymnastics.

So the reverse of that, the gluteals, when they contract, they cause the hip to extend.

That's straightening back out.

Nice example of that is here as we explode outta the blocks in a hundred metre race, the gluteals are contracting really forcefully to straighten that leg at the hip joint.

So let's do another quick check then.

Which of the following is on the anterior or front of your body? Is it: A, the latissimus dorsi; B, the trapezius; C, the biceps; or D, the triceps.

That's right.

It's B, the bicep.

So if biceps here on the front, all of the other muscles on the posterior, the back of your body.

Okay, so that leads really nicely into the first task I'd like you to do today.

So I'd like you to label the upper body and the core with the following muscles.

So we've got the latissimus dorsi, the pectorals, the biceps, the triceps, the abdominals, the deltoids, the trapezius, the gluteals, and the rotator cuffs.

Can you label those up for me and pause the video whilst you do that and come back to me when you're ready? Well done.

Let's check then.

Did you have the rotator cuffs, that muscle just in there sitting on top of the scapular or group of muscles actually.

Then we've got the pectorals on the front.

The biceps in the top of the upper arm.

The abdominals or the six pack, hopefully.

The triceps on the back of the upper arm.

The trapezius, that triangular muscle up on top of your shoulders and into your neck.

The deltoid that muscle on the top of your shoulder.

Latissimus dorsi, particularly important and well developed in swimmers that sheet muscle across the back.

And then the gluteals or the bum.

Well done if you've got all of those correct.

Okay.

Moving on to the second part of today's lesson then where we look at muscles in the lower body and their roles.

So pause the video for a second.

Could you identify these muscles? Yeah, we've got the quadriceps group.

So there's four muscles that make up the quadriceps on the front of our thigh.

Then at the back we've got the hamstring group.

So there's three muscles that make up your hamstrings.

And then the gastrocnemius is that muscle in your calf.

That's really important for pointing your toes.

It's connected by the achilles tendon to your foot.

We've also got the hip flexors in here, and you might be able to feel your hip flexors working when you flex your hip.

So bring your leg up in front of you.

And we've got the tibialis anterior.

So the way I remember that name, it's the tibia is the bone that it sits on top of, and it's at the front of the body.

And another word for front is anterior.

A word for back is posterior.

So to have a look at each of them in action.

So the hamstrings contract and that causes flexion at the knee joint.

You can see how when the muscle pulls, it shortens and that'll cause that flexion of the knee joint.

An example is if you're preparing to kick a ball in rugby, we can see that flex position in that left knee.

The quadriceps contracts to cause extension of the knee joint.

So the opposite contraction.

An example of that would be that follow through of kicking a ball in football.

We can see that right leg there in a fully extended position.

In addition though, we've also got the hip flexors, haven't we that are working hard to bring that leg up into the flex position at the hip.

So both of those muscles are important.

Okay, so the gastrocnemius.

So when that contracts, it causes pointing of the toes or plantar flexion as we know it's called at the ankle joint.

An example of that might be if you are up en pointe, so on your tiptoes in ballet.

In addition, on the anterior side, so on the front of your shin you've got the tibialis anterior, and when that muscle contracts, it dorsiflexes at the ankle.

So you can see here this hurdler with that lead leg up in that dorsiflex position to get over the hurdle.

And you might have come across people that have perhaps got shin splints, and that's sometimes some pain around some of the tendons connected to the tibialis anterior because of lots of road running.

So which of the following is not on the posterior or back side of the body? Is it: A, the gluteals; B, the hamstrings group; C, the quadriceps group; or D, the gastrocnemius.

What do you think? That's right, it's the quadriceps 'cause that's on the front of our thighs, isn't it? Whereas the rest of them are all behind us.

Another quick check, which of the following is responsible for flexion at the knee joint? Is it: A, pointing at the gluteals; B, pointing at the hamstrings; or C, pointing at the gastrocnemius? That's right, it's B.

So flexion at the knee joint is caused or created by the hamstrings group.

Okay, onto the second task then.

So returning to this labelling of the body, but now with the muscles of the lower body, I want you to label up the gastrocnemius, the gluteals, the hamstring group, the quadricep group, the tibialis anterior, the hip flexors, and you'll want to pause the video now whilst you do that and come back to me when you are ready.

Well done.

Let's have a quick look at what you came up with then.

So we've got the hip flexors, that band coming from the hip down towards the knee.

We've got the quadriceps group, that big chunk of four additional muscles on top of the thigh.

Then on the posterior side we've got the gluteus maximus or the gluteals.

We've got the hamstring group and we've got the gastrocnemius or calf muscle.

Then on the posterior side we've got the tibialis.

Sorry, on the anterior side we've got the tibialis anterior.

Okay, that takes us into the third and final part of today's lesson where we look into this idea of antagonistic muscular pairs.

Okay, so here we've got the bicep working and as I mentioned earlier, muscles can only pull, they cannot push.

So when a muscle contracts, it shortens as what we call actin myosin filaments that slide over each other to contract the muscle and shorten it.

And because of that, muscles are connected to bone via tendon so that when they shorten that tendon that's connected on the other side of the joint can pull the bone.

So it's almost like an elastic band connecting it to the other side of the joint.

Okay, and if one muscle's gonna contract to cause that movement to happen, we call that muscle the agonist or the prime mover.

But whilst that muscle's contracting, there's gonna be another muscle, the triceps in this instance, that's relaxing in opposition to that and stretching, its lengthening ready to reverse roles to straighten my arm back out again.

So antagonistic pairs, one causes one movement whilst the other relaxes, and then the other reverses that movement.

Let's have a look at what that looks like perhaps for a bicep curl.

So that during the upward phase the biceps will work as the agonist lifting that weight up and the triceps are acting as the antagonist relaxing in opposition to that.

And then the rolls reverse when we lower the weight back down.

So quick check then.

During the upward phase of a biceps curl, which muscle is working as the antagonist? Is it: A, the biceps; B, the triceps; or C, the deltoid.

That's right.

It's B, the triceps.

Okay, let's have a look for another antagonistic pair.

So we've got here the quadriceps group that operate as an agonist to extend the knee joint.

And meanwhile the hamstrings on the back of the thigh are the antagonist relaxing in opposition.

The roles reverse when we recover the leg back down to the ground.

At the same time when we're kicking that ball, the hip flexes are also gonna act as an agonist, aren't they? To flex the hip joint.

And meanwhile, the gluteus maximus or the gluteals will be the antagonist relaxing in opposition.

As I mentioned earlier, the roles then reverse in the opposite movement.

So when we prepare to kick the ball, it'll be the gluteals contracting as the agonist.

Let's look another pairing.

So as we move up into that plantar flex position, pointing our toes, the gastrocnemius, you can feel it now contracting if you wanted to have a go at that.

So you can feel a gastrocnemius contracting as you point your toes.

And then the tibialis anterior is acting as the antagonist, so it's stretching and lengthening against that.

And then the roles reverse when we lower ourselves back down.

So let's do another quick check.

Which of the following is an example of the triceps acting as the agonist? So where have we got the triceps causing the movement? Is it: A, in that squat; B, as the execution of that chest pass happens in netball; or C, as the leg lifts up into that flexed position? That's right.

It's B, isn't it? So the triceps are the agonist when that elbow joint is straightening.

Okay then, time for you to have a go.

So the final task for today's lesson, I want you to explain how antagonistic pairs work.

And then secondly, I want you to identify at least six major muscles and the movement that they are creating as this sprinter accelerates out of the blocks.

Pause the video now whilst you do that and come back to me so that we can compare answers.

Well done then.

So hopefully you wrote something along these lines: "So the agonist, or the prime mover, contracts to create movement.

Meanwhile, the antagonist relaxes in opposition to this and allows that movement to happen.

When muscles contract, they work with one contracting, the other relaxing and that's known as antagonistic pairs." Secondly, we were asking you to have a bit of a look at this and we can see the right bicep is in a flexed position at the elbow joint.

Meanwhile, the left tricep has extended that elbow.

The front knee there.

So the right knee is in a flexed position with the hamstring group acting as the agonist.

Meanwhile, the quadriceps group has extended the back knee, so the driving out of the blocks happens.

The gluteals is contracted to extend that back hip.

Then we've got the right pectorals contracting as the shoulder adducts.

And meanwhile the left deltoid is slightly abducting that left shoulder.

Well done if you identified all of those correctly.

And we're gonna keep looking at examples of sporting movements and analysing those joints throughout this course.

Okay, that leaves me with just one thing to do and that's to summarise today's lesson.

So we've learned the major muscles that contract to produce movement and that they're located all over the human body.

We've learned that muscles are attached to bones by tendons.

One of the most important tendons in the human body is the achilles tendon that connects the gastrocnemius to the heel.

And when muscles contract and relax, they do so to move bones and work in antagonistic pairs.

So when one muscle contracts known as the agonist or prime mover, the other relaxes known as antagonist.

And we have also learned that the rotator cuff group of muscles help stabilise that shoulder joint to enable lots of movement to happen.

The biceps and triceps are a great example of an antagonistic pair and so are the quadriceps and hamstrings.

But we also talked, didn't we, about the tibialis anterior and the gastrocnemius being a pair and about the hip flexor and the gluteals or the gluteus maximus being a pair.

I hope you've enjoyed today's lesson.

There was an awful lot in there to learn, wasn't there? So you might want to come back and watch it again.

Well done and see you next time.