Rotator cuff muscles

Summary

This script delves into the intricacies of the shoulder's rotator cuff muscles, crucial for swimmers and athletes. It highlights the role of these muscles in securing the humeral head within the glenoid fossa, enabling a wide range of motion. The video explores the functions of the four rotator cuff muscles—supraspinatus, infraspinatus, teres minor, and subscapularis—discussing their attachments, nerve supply, and impact on shoulder stability and movement. It also touches on common injuries and offers exercises to strengthen these muscles, emphasizing the importance of maintaining shoulder health for those with physically demanding activities.

Takeaways

• 🏊‍♂️ The script discusses the importance of shoulder muscles, especially for swimmers, in providing power and stroke length.
• 🤔 The focus is on the rotator cuff muscles, which are crucial for securing the humeral head within the glenoid fossa and preventing shoulder injuries.
• 💪 There are six scapular humeral muscles, including the deltoid and teres major, which are not part of the rotator cuff but play a role in shoulder movement.
• 🔍 The rotator cuff muscles include supraspinatus, infraspinatus, teres minor, and subscapularis, which are essential for supporting the shoulder joint.
• 🏋️‍♀️ The supraspinatus muscle initiates the abduction of the upper limb, followed by the deltoid and trapezius muscles.
• 🔄 The rotator cuff muscles are responsible for both medial and lateral rotation of the humerus, with specific muscles contributing to each movement.
• 🚫 The rotator cuff muscles do not contribute to the adduction of the humerus, which is handled by other muscles like latissimus dorsi.
• 🤕 Overuse injuries are common in the rotator cuff muscles due to their small size and the large range of motion they support.
• 🏥 The supraspinatus tendon can become inflamed, leading to issues like tendonitis, especially when passing through the narrow space under the acromion.
• 💡 Strengthening the rotator cuff muscles is essential for those who use their shoulders extensively, such as swimmers, and can be done using light resistance like elastic bands.

Q & A

What is the main purpose of the rotator cuff muscles in the shoulder?

The primary function of the rotator cuff muscles is to support the humeral head within the glenoid fossa, maintaining the shoulder joint's integrity and stability.

How many muscles form the rotator cuff, and what are their names?

There are four muscles that form the rotator cuff: supraspinatus, infraspinatus, teres minor, and subscapularis.

Why are the rotator cuff muscles prone to overuse injuries?

The rotator cuff muscles are prone to overuse injuries because they have to pass across a small space, which can lead to inflammation and tendonitis, especially due to their critical role in stabilizing the shoulder joint.

What is the role of the deltoid muscle in the shoulder joint?

The deltoid muscle plays a significant role in holding the humerus into the joint, aiding in abduction, flexion, extension, medial rotation, and lateral rotation of the humerus.

How does the supraspinatus muscle contribute to the movement of the arm?

The supraspinatus muscle initiates the abduction of the upper limb, allowing the arm to move away from the body.

What is the difference between the teres major and teres minor muscles in terms of their function and innervation?

Teres major is a medial rotator of the humerus and is innervated by the lower subscapular nerve, while teres minor is a lateral rotator and is innervated by the axillary nerve.

Which nerve innervates the infraspinatus and supraspinatus muscles?

Both the infraspinatus and supraspinatus muscles are innervated by the suprascapular nerve.

What is the function of the subscapularis muscle in the shoulder joint?

The subscapularis muscle, located anteriorly, contributes to medial rotation of the humerus, and its main function is to hold the humeral head in place within the glenoid fossa.

How can one strengthen the rotator cuff muscles?

Strengthening the rotator cuff muscles can be achieved through exercises using elastic bands, focusing on medial and lateral rotation movements to engage the respective muscles effectively.

What is the significance of the brachial plexus in relation to the shoulder muscles discussed in the script?

The brachial plexus is significant as it provides the nerves that innervate the shoulder muscles discussed, including the suprascapular, axillary, and subscapular nerves.

Why is it important to maintain good shoulder posture and muscle strength for individuals who use their shoulders frequently?

Maintaining good shoulder posture and muscle strength is crucial for individuals who frequently use their shoulders to prevent joint and muscle damage, ensuring effective use of the rotator cuff muscles and overall shoulder joint health.

Outlines

00:00

🏊‍♂️ Swimming and Shoulder Muscles

The speaker discusses their training phase as a bass, highlighting the fatigue and an upcoming test race. They emphasize the importance of the shoulder muscles, particularly the rotator cuff muscles, which support the humeral head within the glenoid fossa. The speaker mentions the need for secure joint movement and the potential for overuse injuries in these muscles. They plan to explore the rotator cuff muscles in a lab setting, using a model to demonstrate the muscles' roles in abduction, flexion, extension, and rotation of the humerus.

05:02

💪 Deeper Look at Rotator Cuff Muscles

The speaker removes the deltoid muscle from the model to reveal the rotator cuff muscles, which are crucial for shoulder stability and movement. They identify the supraspinatus, infraspinatus, teres minor, and teres major muscles, explaining their roles in medial and lateral rotation of the humerus. The speaker also discusses the innervation of these muscles, noting that supraspinatus and infraspinatus are innervated by the suprascapular nerve, while teres minor and deltoid are innervated by the axillary nerve. The teres major is innervated by the subscapularis nerve, which is also connected to the subscapularis muscle.

10:04

🤔 Understanding Muscle Functions and Injuries

The speaker delves into the functions of the rotator cuff muscles, focusing on their role in stabilizing the humerus within the glenohumeral joint. They explain that these muscles are not involved in adduction but are essential for maintaining joint integrity. The speaker also discusses the potential for overuse injuries, particularly tendonitis, due to the muscles' location and function. They highlight the importance of strong rotator cuff muscles for those who frequently use their shoulders, such as swimmers, and suggest exercises using elastic bands to strengthen these muscles.

15:06

🏋️‍♂️ Strengthening the Rotator Cuff

The speaker concludes by emphasizing the importance of maintaining strong rotator cuff muscles, especially for those who engage in activities that heavily utilize the shoulders. They describe exercises that can be performed using elastic bands to strengthen these muscles, focusing on medial and lateral rotations of the humerus. The speaker also mentions the innervation of the rotator cuff muscles by the brachial plexus, which is crucial for their function. They look forward to discussing more about the shoulder in the next session, promising to cover topics such as the shoulder's baring.

Keywords

💡Bass training

Bass training refers to the process of training the lower part of the body, particularly the legs, which is crucial for endurance and strength in sports. In the video, the speaker mentions reaching the end of their bass training phase, indicating a focus on leg muscle development, which is essential for activities like swimming and racing.

💡Fatigue level

Fatigue level is the degree of tiredness or exhaustion experienced by an individual, often as a result of physical or mental exertion. The script mentions a high fatigue level, suggesting that the speaker is experiencing significant tiredness due to their training regimen, which is a common challenge for athletes preparing for races.

💡Test race

A test race is a competitive event used to gauge an athlete's performance and readiness for a season. The speaker is planning to participate in an early-season test race to evaluate their current form and training progress, which is a common practice in sports to determine how well the preparation is translating into performance.

💡Shoulder mobility

Shoulder mobility refers to the range of motion of the shoulder joint, which is critical for activities that require extensive arm movement, such as swimming. The script discusses the importance of shoulder mobility for swimmers, highlighting the need for a wide range of movement to execute powerful and efficient strokes.

💡Humeral head

The humeral head is the rounded end of the upper arm bone (humerus) that fits into the shoulder joint. The script emphasizes the importance of securing the humeral head within the joint, which is crucial for maintaining shoulder stability and preventing injuries during physical activities.

💡Rotator cuff muscles

The rotator cuff muscles are a group of four muscles and tendons that surround the shoulder joint and are responsible for its stability and rotation. The script explains that these muscles support the humeral head within the glenoid fossa, highlighting their role in preventing shoulder injuries due to overuse.

💡Scapular humeral muscles

Scapular humeral muscles are those that connect the scapula (shoulder blade) to the humerus (upper arm bone). The script identifies six such muscles, including the deltoid and teres major, which are essential for movements of the arm and shoulder stability.

💡Supraspinatus

The supraspinatus is one of the rotator cuff muscles that originates on the supraspinous fossa of the scapula and inserts on the greater tubercle of the humerus. It plays a key role in starting the abduction of the arm, as mentioned in the script, and is prone to overuse injuries due to its location and function.

💡Infraspinatus

The infraspinatus is another rotator cuff muscle located below the spine of the scapula. It is involved in lateral rotation of the humerus, as described in the script, and is essential for the proper functioning of the shoulder joint.

💡Teres minor and major

Teres minor and teres major are muscles associated with the rotator cuff and shoulder movement. Teres minor aids in lateral rotation of the humerus, while teres major contributes to medial rotation, as explained in the script. They have different nerve supplies, indicating their distinct roles in shoulder function.

💡Subscapularis

The subscapularis is the final muscle of the rotator cuff and is located on the anterior side of the shoulder joint. It is responsible for medial rotation of the humerus, as mentioned in the script, and is crucial for maintaining the stability of the shoulder joint.

💡Brachial plexus

The brachial plexus is a network of nerves that originates from the spinal cord and provides motor and sensory function to the arm. The script mentions the brachial plexus in relation to the innervation of the shoulder muscles, emphasizing its importance for muscle function and movement.

Highlights

The importance of shoulder muscles in swimming and other activities that require a lot of shoulder movement.

Discussion of the big muscles of the shoulder and their role in providing maximum power and a long stroke in swimming.

The role of the humeral head in securing and holding the shoulder joint, and the importance of its stability.

Introduction to the six scapular humeral muscles, including the deltoid and teres major.

The main job of the rotator cuff muscles is to support the humeral head within the glenoid fossa.

The rotator cuff muscles are prone to overuse injuries due to their small size and large job in stabilizing the shoulder.

The lab session focuses on the rotator cuff muscles of the shoulder, highlighting their importance in maintaining shoulder stability.

The use of a model to demonstrate the muscles and their functions, including the deltoid and its role in holding the humerus into the joint.

The role of the supraspinatus muscle in starting the abduction of the upper limb.

The infraspinatus muscle's role in lateral rotation of the humerus.

The teres minor muscle's contribution to lateral rotation, contrasting with teres major's medial rotation.

The subscapularis muscle's role in medial rotation and its deep position beneath the scapula.

The different innervation of the rotator cuff muscles, with supraspinatus and infraspinatus being innervated by the suprascapular nerve.

The importance of the rotator cuff muscles in holding the humerus in place and their role in the glenohumeral joint.

The practical application of strengthening the rotator cuff muscles using elastic bands for exercises.

The explanation of how the rotator cuff muscles contribute to the stability and function of the shoulder joint.

The summary of the rotator cuff muscles' functions, including their role in rotation and stabilization of the humerus.

Transcripts

so I'm reaching the end in my bass

training phase fatigue level high and

racing this weekend as well which is the

test race early season to see how things

go but I've just been swimming in the

pool again at lunchtime my usual daily

swim and thinking more about the

shoulder so we looked at the big muscles

of the shoulder last week and of course

I think about the big muscles a lot when

I'm swimming and how I'm gonna use those

muscles to get maximum power and get a

nice long stroke and move myself and

that sort of thing but something that's

also really important to swimmers and

other people who use their shoulders a

lot is not just the wide range of

mobility that we have but how is the

humeral head secured and held within

that joint because it's it's quite an

open face which is great means you've

got a wide range of movement but you

need to hold that humerus securely there

are six scapular humeral muscles we

talked about a couple last week deltoid

and we talked about teres major but the

other four which come up all the time of

the rotator cuff muscles so the rotator

cuff muscles their main job is to

support the humeral head within that

glenoid fossa and to keep that shoulder

together and those muscles are

reasonably big but they have to pass

across a small space and they get rather

small and tenderness and a number of

people will have problems with their

rotator cuff muscles because this more

and they've got quite a big job to do

and they suffer from overuse injuries

and that sort of thing so let's go in

the lab I'll take a break from marking

exam papers let's go to the lab and talk

about the rotator cuff muscles of the

shoulder briefly all right let's go all

right then we can use this guy no

photography unless you're me I can do

that no food and drink I can't do food

and drink either

we'll use you but I've also got a very

nice upper limb model move so I I really

like this model this is another one of

Rudy's models these are beautifully made

and this is kind of kind of a rubberized

plastic some bits are harder than others

I would love more models like this I'd

love a lower limb model like this as

well just to show musculoskeletal stuff

but it'd be nice if the muscles were

nice and stretchy and this one it seems

like maybe it's got a little bit harder

over time but it is prone to falling

apart when you touch it I think puts

students off a little bit and it needs

to be able to pain putting back together

but then that's all part of the learning

process right which is why we have a bit

left over here so we were looking on the

the model last week of the of the large

muscles of the shoulder region that tend

to act on the upper limb and move the

humerus and what have you and we looked

at deltoids and here's the deltoid

muscle so I say there are there are six

scapula humeral muscles so summing that

is to say six muscles passing between

the scapula and the humerus and we

looked at the deltoid we talked about

how the deltoid holds the humerus into

the joint into the infra glenohumeral

joints when you're carrying something

heavy the the weight is carried from the

hto skeleton through trapezius and other

muscle through the scapula and then from

the scapula and the clavicle down to the

humerus and everything's held together

right and that's one of the roles of the

deltoid muscle

now I mentioned supraspinatus so

superspinatus as I said start off the

abduction of the upper limb and then the

deltoid muscle can take over and then

trapezius takes over to rotate the

scapula do you remember and I mentioned

that the deltoid muscle can also do

flexion and extension of the humerus at

the glenohumeral joint what I probably

didn't mention is about row

right we also have medial rotation and

lateral rotation so if you think about

it this is the humerus that's rotating

here at the glenohumeral joint right yes

the humerus is rotating like this so so

this is what we've got so this is medial

rotation and this is lateral rotation

and you can see how the the humerus is

rotating here so it's rotating inwards

and outwards now most of that is

occurring up here and these multi penny

fibers of the deltoid muscle can

contribute to this you can imagine how

the anterior muscles can pull this way

so they can add they can contribute to

the medial rotation and how these

posterior fibers here you can pull the

other way and contribute to lateral

rotation but there are some deeper

muscles when we take off the deltoid

muscle then we'll see the rotator cuff

muscles and supraspinatus is one of them

so we take off deltoid the other always

heavier than the other muscle that we

talked about was teres major here so

terror is major we said runs from the

scapula to the humerus then can you see

how this is a right upper limb so

there's the thumb so this is it this is

a right upper limb and can you see how

his teres major here and I said the

teres major is forming the posterior

border of the axilla right under here

but do you see how it's running from the

scapula but then it's running

to the anterior part of the humerus let

me take off bicep so you can see a

little bit more easily no you see I was

running to the anterior part of humerus

that means that if this muscle contracts

it's going to pull the humerus this way

isn't it so teres major then is also a

medial rotator of the humerus

so deltoid and teres major our muscles

linking the scapula and the humerus but

they're not rotator cuff muscles the

rotator cuff muscles are deeper or

closer to the glenohumeral joint and

they they have another function and

there are four of those so we see one

here two up here and then three and

there's a fourth here but it's actually

difficult to separate these two muscles

so here is supraspinatus now this is the

scapula and this is the spine of the

scapula here turn you around so that

matches so here's his right arm here's

the scapula here's the spine of the

scapula here so this this fossa this

groove here is filled with supraspinatus

but there's a hole through here so

supraspinatus is attached to the scapula

superior to this this spine here

but then the tendon passes through this

gap this is the acromion like the

highest part the acromion akropolis the

highest part of the scapula the bit you

have the bony bit you can feel up here

it passes underneath there and inserts

into the humerus and this is this can

know this muscle then is able to pull on

the humerus up here and that starts off

abduction of the humerus right which is

why I say supraspinatus then deltoid and

then trapezius

because this because of overuse injuries

with the shoulder if this tendon gets

inflamed is passing through a fire a

fairly small gap so they in flames it

swells it gets even more annoyed and we

tend to have a bit of a problem him and

some people get tendonitis of that

attendant so if that supraspinatus up

here and this is the spine

then what's this muscle here

infraspinatus very good well done so

yeah this is infraspinatus inferior to

the spine of the scapula and you can see

again how this is passing out also to

the head of the humerus here right now

as we are posterior if you if you

shorten this muscle then what's going to

happen to the humerus all right so the

muscles running across here to the

humerus here it's going to cause lateral

rotation yeah so if they're not if

infraspinatus contracts it's going to

pull the humerus around this way and

it's going to cause lateral rotation now

the muscle down here if this is teres

major this muscle here is teres minor it

is difficult to tell the two apart when

you're dissecting you can separate the

two muscles they are distinct muscles

good to start with they look like one

single muscle but this is teres minor

here so this is also running from the

scapula to the humerus around here so

terror is minor then if you can track

that muscle is also going to give

lateral rotation so teres minor will

give lateral rotation the teres major

here because it passes to the other side

will do the opposite will do the medial

rotation tricky huh the other thing

about these two muscles is they have

different innovation supraspinatus and

infraspinatus are both innovated by the

suprascapular nerve but teres minor is

innervated by the auxilary nerve the

same nerve innervates the deltoid muscle

confused

the teres major is innervated by the

subscapular to have we're making it

worse my probably sorry so these two

muscles are innervated by the

suprascapular nerve

whereas this muscle is innervated by the

axillary nerve which shows that these

two muscles are the separate things

where they're two muscles they have

separate connective tissue surrounding

them and they have different innovation

all of those nerves by the way come from

the brachial plexus which of course is

very nearby because it's running through

the eggs illa so there's supraspinatus

infraspinatus and teres minor their

fourth and final muscle of the rotator

cuff group is this muscle here this is

subscapularis so if I turn the skeleton

around as well we're now looking at this

scapula here right so this muscle is is

underneath here all right so I'm not

sold underneath there which is tricky in

it so it sits between the ribs and the

scapula right so this is subscapularis

is deep to the scapula you can see how

it's running from the deep surface of

the scapula again to the humerus and

it's inserting here now I took the

biceps brachii muscle off but you can

see well you can see how where that

attach is therefore tape yeah so we take

biceps off and you can see this is deep

the biceps there's the long head there's

the short head that means that the long

head is running through this groove here

this means that these fibers are in 13

so the lesser tubercle up here and this

medial edge of the bicipital groove here

so if the fibers are running this way

and they put on the humerus what's going

to happen it's going to give medial

rotation so subscapularis anteriorly

will give medial rotation

and the other guys post eerily will give

lateral rotation and superspinatus will

give abduction so here's triceps so

we're looking at the posterior arm tur

here's the spine of the scapula here's

the clavicle up here here's

supraspinatus running through there

there's the acromion of the scapula

there so supraspinatus is running

inferior to that and inserting to the

humerus up here here is infraspinatus

and here is teres minor here and there

is teres major these tendons are all

inserting into different facets of the

greater tubercle of the humerus up here

so here's the head of the humerus here

here's that bicep it'll groove third

subscapularis inserting here here's

supraspinatus the infraspinatus and

there's teres minor okay so those are

the muscles those are their attachments

and those are the movements that they

can perform but the most important

function is that they're holding the

humerus in place they're holding the

humerus into the glenohumeral joint and

into the scapula and the the fibers of

the tendons actually merge and blend and

support the connective tissues of the

glenohumeral joint of the snow of your

capsule and we'll have you so they're

forming the structure of the joint their

tone keeps the head of the humerus into

the scapula so if one of these muscles

is damaged then that going to reduce the

strength and the function and the

effectiveness of this joint also because

these fibers are inserting so high up

into the humerus they're not involved in

adduction of the humerus so if if we

talk about abduction like this these

rotator cuff muscles are not going to

bring the humerus

back to the body because there and

they're pulling on the head they pull on

the head they're just pulling the

humerus back into the glenohumeral joint

right for adduction for using you know

latissimus dorsi and all these other

guys right that we talked about in the

last video so the rotator cuff muscles

can rotate the humerus and more

importantly they're holding this whole

joint together so it's important that

you have strong rotator cuff muscles

particularly if you're using your

shoulders a lot and it's important to

you know keep your shoulders in a good

position so that you're using with your

rotator cuff muscles effectively if your

shoulders you know start to get pulled

forward and you you're performing strong

movements and you'd like you to damage

the joint and damage the muscles you you

can strengthen your rotator cuff muscles

very simply you don't tend to need to

use a lot of weight things use elastic

bands right so as you hop on to this and

then you do you keep your arm nice and

straight and square and against the

force you do medial rotations you just

rotating the humerus and then yeah you

can feel nice little burn anteriorly

so you get so again subscapularis here

army we've medial rotation if you put

the hand the other way and then you're

pulling in the other direction so you

see how the humerus there is rotating so

then with lateral rotation exercises

we're hitting the posterior muscles I

can really feel that there we're using

infraspinatus and teres minor and that's

how you keep your rotator cuff strong

something like that anyway okay so there

are six muscles linking the scapula and

the humerus four muscles form the

rotator cuff the muscles of the rotator

cuff inserts high into the head of the

humerus so they can rotate the humerus

but their most important function is

holding the head of the humerus into the

glenoid fossa into the glenoid cavity

and hold that glenohumeral joint

together subscapularis is innervated by

the upper and lower subscapular nerves

supraspinatus and infraspinatus are

innervated by the suprascapular nerve

teres minor is innervated by the

axillary nerve as is the deltoid muscle

teres major is also innovated by the

lower subscapular nerve and those are

all branches of the brachial plexus

unsurprisingly because it's running

through the axilla okay so that's the

that's the rotator cuff and those are

the deep muscles of the shoulder make

sure you can identify them

make sure you remember how they insert

into the humeral head and then you'll

hopefully remember which way they rotate

the humerus all right what we'll do next

week it's plenty of stuff doing the

shoulder maybe I'll still be

enthusiastic about the shoulder we'll

find some males talk baring the shoulder

okay thank you very much see you next

time

you

[Music]