Lesson video

Hello and welcome to today's lesson.

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

So this lesson's called Voluntary muscles and antagonistic pairs, and it comes from the unit Anatomy and physiology: the musculoskeletal system.

It's one of my favourite lessons because it's our chance to learn the names of the major muscles all over the body, but also what happens when those muscles contract, so what they cause to happen and how those muscles work together to create opposite movements.

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

There's lots of keywords that we're going to be going through in today's lesson, but the important ones to be aware of are: agonist, or prime mover, antagonist, antagonistic pairs, and tendons.

You might want to pause the video now and make a quick note of what each of those keywords means, but we will be revisiting them through the lesson.

Okay, so today's lesson is broken up into three parts.

We've got voluntary muscles and antagonistic pairs as the holistic title, and then we're going to break that down to look at the major muscles in the upper body, then the major muscles in the lower body, and then finally explaining how those muscles work together in antagonistic pairs.

I hope you're ready.

Let's get going.

So, the human body is made up of lots of skeletal muscles, it's covered in them, and they're under our voluntary control, which means that when we send a signal from our brain to tell those muscles to contract, then that's what happens.

And when we tell a muscle to contract, it shortens in length, and that's due to the actin and myosin filaments that make up a muscle fibre, reaching over each other to shorten.

So this allows us to complete everyday tasks such as boiling the kettle, walking around, but also to complete complex movements in sport.

Can you point out and name any of your muscles? Pause the video for a second and see if you can name any before we walk our way through them.

Okay, let's look at the muscles of the upper body first then.

So we've got the deltoids, that muscle on the top of the shoulder.

The pectoralis major, one of the pectoral muscles in the chest.

The biceps, which is actually made up of two muscles, the biceps on the front of the upper arm.

And then on the back we've got the trapezius, that big triangular muscle across your shoulders.

The triceps, which is actually three muscles in the back of your arm.

And then the latissimus dorsi there, which is that big sheet muscle, almost makes that V shape up the back.

Okay, let's delve into those in a little bit more detail then.

So when the deltoid contracts, this muscle on the top of our shoulder, it causes abduction of the shoulder movement up to the side.

If you abduct your shoulder with me now, you'll feel that that muscle is tense.

If you are holding a heavy weight, it would be even more tense, wouldn't it? And a nice sporting example of that muscle in action is if a goalkeeper reaches out to the side as they reach to save a shot in the corner of the net.

Let's look at the biceps next.

So when the biceps contracts, it causes flexion at the elbow joint, probably the most known movement.

And for example here we can see this rock climber, they're in the extended position at the moment at the elbow, but as they pull themselves up, they'll be flexing that bicep muscle in order to move up the rock face.

Then the latissimus dorsi, so that big v-shaped muscle across the back.

So when that contracts, it pulls your arms down to the side like that.

And we can see that in the pool phase of this is someone swimming butterfly, but also when swimming freestyle, so front crawl.

So let's do a quick check then.

Which of the following is responsible during the preparation phase of a chess pass in netball? Is it A, the pectoralis major; B, the biceps; C, the triceps; or D, the deltoid muscle? That's right, it's the biceps.

So as we bend the elbow to hold the ball close to the chest, it's the bicep muscle that's contracted to cause that movement.

Shall have a look at the trapezius muscle then, it sits on top of the latissimus dorsi, and that muscle causes abduction, movement up of the shoulder joint.

A really nice example of that is when throwing a discus in athletics.

You can see this performer here in that abducted position.

And then let's look at the triceps.

So that one's the back of my upper arm.

And when that muscle contracts, we extend our elbow joint.

Nice example of that, we can see this tennis player as they throw the ball up.

So with that ball toss hand, we can see it's in that extended position.

And meanwhile the right arm is in a flexed position, but it will extend as it strikes the ball.

So often really important to talk about is it in this snapshot moment or when this A to B movement is happening.

Okay, next up we've got our pectoralis major.

So when our pectoralis major contracts, it causes adduction of the shoulder joint.

So those pectoral muscles, one of which is called the pectoralis major, pulls that arm down to the side and we can feel it contracting when that happens.

A nice example of that is the downward phase of a golf swing.

You can really see the pectoralis major working there.

Okay, let's do another quick check then.

Which of the following is responsible for adduction at the shoulder? Is it A, the pectoralis major; B, the biceps; C, the triceps; or D, the deltoid? That's right, the pectoralis major is the one that pulls the shoulder joint back down to the midline of the body.

Okay, let's look at some muscles in the core next.

So what have I highlighted here? Well, we've got the abdominals, or the six pack.

We've got the external obliques, so on the outside of those sometimes referred to as the love handles.

And then we've got the gluteus maximus, which is one of the muscles in the gluteal group which makes up your bum.

Okay, so let's look at those abdominals first.

So when they contract, they cause flexion of the spine and also at the hip joint.

So if I get into that tucked position of a somersault or a forward roll in gymnastics, my abdominals will definitely be contracting.

Meanwhile, I've got those external obliques on the outside of my abdominals, and they cause that trunk twisting movement, so leaning down to the side.

So we can see here a lovely example of a goalkeeper who's reaching out to the side to get the ball.

So their obliques will be working really hard to achieve that.

And then we've got the gluteus maximus, so that big gluteal muscle on the back of the bum.

And when that contracts, it will cause hip flexion.

A nice example of that is exploding out of the blocks in a hundred metre race.

We can see that large bum muscle will be contracting to straighten that back leg.

Okay, so let's do another quick check then.

Which of the following is on the anterior or front side of the body? Is it A, the latissimus dorsi; B, the trapezius; C, the biceps; or D, the triceps? That's right, it's B, the biceps.

They're on the front of the body, whereas all the rest are on the posterior, the backside of your body.

Okay, that brings us to our first practise task of the day.

I'd like you to have a go at labelling the upper body and the core with the following muscles.

Can see them there in the table, so the lats, or latissimus dorsi, the pecs, or pectoralis major, biceps, triceps, abdominals, sometimes called the rectus abdominis, external obliques, deltoids, trapezius, and the gluteals, or the gluteus maximus as you need to refer to it.

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

Okay, let's compare answers, shall we? So we've got the pectoralis major in the front of the chest there.

Underneath that we've got the biceps in the upper arm.

And below the pecs, we've got the abdominals, so the six pack.

We've got the triceps there in the top of the upper arm, on the back of it.

The trapezius, muscle at the top of your shoulders.

Deltoids on top of your shoulder, so before it feeds into the trapezius.

The latissimus dorsi, that v-shaped muscle across the back.

And the gluteus maximus, or gluteals or bum muscles.

And then we've got the external obliques there as well, haven't we, on the outside of the abdominals.

Hope you got all of those, and we'll certainly be spending some more time with all those muscles in future lessons.

Okay, let's move into the second part of today's lesson and where we look at major muscles in the lower body.

I wonder if you know more or less of these.

So what are the names of these ones? Well, we've got the quadriceps in front of the thigh.

We've got the hamstrings on the back.

We've got the gastrocnemius, or calf muscle.

And then the hip flexors, so also on the front there underneath the quadriceps, responsible for flexing the hip.

And the tibialis anterior is kind of on the shin there.

So I remember that because the word tibia is the bone that's there, and anterior means front.

So tibialis anterior is the muscle at the front of your shin.

So let's have a look at what those muscles do then.

So the hamstrings contract to cause flexion at the knee joint.

Nice example of that there is when preparing to kick a conversion, this left leg is in a fully flexed position at the knee joint.

The quadriceps contracts to cause extension of the knee joint.

An example of that would be the follow through of kicking that ball.

So that right leg there is in a extended position at the knee joint in kicking the ball.

In addition to that, on the front or on the anterior side, we've got the hip flexors, and they're working really hard to bring up that flexion at the hip joint.

So there we have it, executing the kick of a football, the movement of the hip joint is flexion and it's caused by the hip flexors.

The gastrocnemius then, so that causes you to point your toes or plantar flex the ankle joint.

An example of that is being on point or up on your tiptoes in ballet.

And we do it in so many sports, don't we, where we get up on our tiptoes.

In addition, on the anterior side, we have the tibialis anterior.

So these cause dorsiflexion at the ankle.

For example, we've got that picture there of the hurdler where they're in that dorsiflex position where the lead leg is pulled up in front to clear the hurdle.

So then, let's do a quick check.

Which of the following is not on the posterior or backside of the body? Is it A, gluteus maximus; B, the hamstrings; C, the quadriceps; or D, the gastrocnemius? Have a little think.

That's right, the quadriceps are on the front of the thigh, aren't they? Whereas all the rest of those muscles are on the posterior side.

Another quick check.

Which of the following is responsible for flexion at the knee joint? Is it A, gluteus maximus, or gluteals? Is it B, a hamstring group? Is it C, the gastrocnemius? Which one does flexion at the knee joint? That's right, it's B, isn't it, the hamstrings.

So, second practise task, we can bring back out that human body and label the lower body with gastrocnemius, the gluteus maximus, the hamstrings, the quadriceps, the tibialis anterior, and the hip flexors.

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

Okay, let's compare answers then.

So we've got the hip flexors, that band down the front there.

Quadriceps all surrounding the hip flexors.

Got the gluteals, gluteus maximus, the bum muscle.

You've got the hamstrings, the hamstring group.

The gastrocnemius below that.

And the tibialis anterior on the front of the shin.

How well did you do with that one? Okay, and that brings us nicely into the third part of this lesson where we'll start to look at how some of those different muscles work in antagonistic pairs to help us move.

So here we've got a bicep muscle, and we know that muscles can only pull, they cannot push.

So when a muscle contracts, it shortens in length and that's because of those actin and mycin filaments that slide over each other to shorten the muscle.

They kind of grab and hook and pull to shorten that muscle.

And because of that, muscles, when they're connected to bone via a tendon, it enables that movement to happen.

So if I look here, my bicep's muscle is connected via a tendon across this elbow joint.

So when I contract my bicep, that tendon will pull to create a shortening and flexion at the elbow.

So I'm in this position, aren't I? And my muscles need to team up because I don't want to stay in this position forever.

So one muscle contracts, it's called the agonist or prime mover.

And whilst it's contracted, in this instance my biceps, my triceps will have relaxed in opposition to it.

And we refer to the triceps as the antagonist in that situation.

So when we perform the upward phase of that bicep curl, it'll be the bicep working as the agonist, flexing the elbow to lift the weight.

Meanwhile, the triceps acts as the antagonist and relaxes in opposition.

And then when we want to lower the weight back down again, the roles will reverse.

Let's do a quick check.

So during the upward phase of a bicep curl, which muscle is working as the antagonist? Is it A, the biceps; B, the triceps; or D, the deltoid? That's right, it's the triceps, isn't it, that are the antagonist, because the biceps are working as the agonist.

So have a look at the leg now.

So if we kick a ball, the quadriceps will be working as the agonist to extend or straighten the knee joint.

And meanwhile, the hamstrings act as the antagonist, so they'll relax in opposition to that movement.

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

At the same time when we're kicking that ball, the hip flexors will be working as an agonist to flex at the hip joint.

And we know that the hip flexors' antagonistic pair is the gluteus maximus.

So meanwhile, the gluteus maximus will act as the antagonist and relax in opposition.

And those roles will reverse if you are preparing to kick the ball.

So you've got to think about, is it the preparation or the execution phase that you are talking about? Next one, when we point our toes, so the gastrocnemius acts as the agonist to plantar flex the ankle joint.

And in opposition to that, the tibialis anterior will be stretching in opposition to that.

So it's working as the antagonist, it's relaxing and stretching out.

Again, those roles will be reversed as you lower yourself back down.

Okay, so let's do another quick check.

Which of the following is an example of the triceps acting as the agonist? Is it A, in that deep squat position about to stand up? Is it B, the netballer who's straightening their arms? Is it C, the person who's in that hip flexion position? Well done.

I'm sure you got that one right.

So the triceps are the muscles in the arm acting to execute throwing a chest pass.

Okay, that brings us into our last task of today's lesson.

I'd like you to explain how antagonistic pairs work.

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

Pause the video whilst you do that and come back to me when you are ready.

Well done.

So hopefully you said something along these lines.

The agonist, or prime mover, contracts to create movement.

Meanwhile, the antagonist relaxes in opposition to allow this movement to happen.

When muscles work together in this way, they are called antagonistic pairs.

And then the second part of this question, hopefully you've identified a few muscles.

For example, the right biceps has flexed that elbow up in front.

And meanwhile, the left triceps have extended that elbow out behind.

So that's the position we're in there.

The front knee is flexed, with the hamstring acting as the agonist.

And meanwhile, the quadriceps has extended the back knee.

The gluteus maximus is contracting to extend the back hip.

And meanwhile, the right pectorals is contracting as the shoulder moves into that adduction position.

Finally, the left deltoid abducts the left shoulder up a little bit to the side, not too much, because we don't want it flailing arms out to the side, but it is slightly abducted.

Well done if you got all of those, or perhaps you looked at some different muscles in that sprinter.

Maybe you looked at the plantar flexion being done by the gastrocnemius, for example.

Okay, last up then, just a chance to summarise today's lesson.

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

And these are called skeletal muscles.

Muscles attach to bones via tendons, and that's what enables them to pull at the joint to create movement.

When one muscle contracts, another one is relaxing in opposition to that, and that's called antagonistic pairs.

So as one muscle contracts or shortens, it's called the agonist or prime mover, and the other is relaxing the antagonist in opposition.

Examples of antagonistic pairs include the following: so the biceps and triceps for flexion extension at the elbow.

The quadriceps and hamstrings for flexion extension at the knee.

The gastrocnemius and tibialis anterior for plantar flexion and dorsiflexion at the ankle.

And the hip flexors and the gluteus maximus for flexion and extension at the hip.

Hope you got those ones nailed, and I'm sure we'll visit them again in other lessons.

Thanks for joining me today, I hope you enjoyed it, and I'll see you again next time.