Unit 1| Section 1| Anatomy and physiology for exercise

Welcome to ‘anatomy and physiology for exercise’.

When working with individuals in a health and exercise-related environment, it’s important to

be familiar with the underlying anatomical and physiological principles of exercise. There

are eight learning outcomes for this unit:

Understand the structure and function of the circulatory system, the respiratory system, and

the skeleton.

Understand the joints in the skeleton, the muscular system, and the life-course of the

skeletal system and its implications for special exercise populations.

And, finally, understand energy systems and the nervous system and their relation to

exercise.

You can find out how to navigate this unit and how everything works by pressing the ‘help’

button at the bottom of the screen, which is the one with the ‘question mark’ icon on it.

We hope you enjoy your studies.

Unit 1| Section 1| The structure and function of the circulatory system

In this section you will be guided through: the location, function and structure of the heart,

and the flow of blood through it; systemic and pulmonary circulation; the structure and

functions of blood vessels; and the definition of blood pressure and its classifications.

Unit 1| Section 1| Location and function of the heart

The heart is a muscular pump located in the upper chest, just left of centre, behind the

sternum. It sits between the lungs in a specially designed cavity. Its primary purpose is to

pump blood to the lungs and also around the rest of the body.

Blood is essential to life and without it the tissues would be starved of oxygen and nutrients,

while waste products would accumulate. The bloodstream is a closed circulatory loop and

needs a mechanism to maintain the flow; this is the heart’s role. It’s vital to sustaining life

and so is referred to as one of the ‘vital organs’.

Unit 1| Section 1| Anatomy of the heart

The heart consists of four chambers: the upper two smaller chambers are called atria, the

two larger, lower chambers are called ventricles. Blood always travels from A to V

(alphabetically). The ventricles have thicker more muscular walls than the atria, as they are

required to push blood out with sufficient pressure to pass through the whole body.

Unit 1| Section 1| Movement of blood through the heart

Blood enters the heart via the left and right atria, where it is pushed into the ventricles before

being forcefully ejected in to the body’s tissues.

Left atrium: receives oxygen-rich blood from the lungs via the pulmonary vein.

Left ventricle: receives blood from the left atrium, before ejecting it into the aorta (main

artery) to supply the rest of the body’s tissues with blood and oxygen.

Right atrium: receives returning, deoxygenated blood from the body’s tissues via the

superior and inferior vena cava (main veins). This is then pumped into the ventricle.

Right ventricle: receives blood from the left atrium, before ejecting it into the pulmonary vein

on its way back to the lungs, where it will receive fresh oxygen and offload unwanted carbon

dioxide.

Unit 1| Section 1| Systemic and pulmonary circulation

The cardiovascular system is made up of the pulmonary and systemic circulations. The

pulmonary circulation is the blood flow from the right ventricle to the left atrium, whereas the

systemic circulation describes the flow of blood from the left ventricle to the right atrium via

the tissues of the body.

Pulmonary circulation is the blood supply from the right ventricle to the left atrium via the

lungs. Blood flow to the lungs passes through the pulmonary artery returning to the heart via

the pulmonary vein. Systemic circulation carries blood from the left ventricle to the tissues

via a large artery called the aorta. Blood returns to the right atrium via a large vein called the

vena cava. To accommodate blood flow from both the upper and the lower body, the vena

cava is comprised of both superior and inferior portions.

Unit 1| Section 1| Pulmonary circulation

Pulmonary circulation involves the blood flow between the heart and the lungs. So starting in

the heart, blood leaves the right ventricle, through the pulmonary artery, reaches the lungs,

leaves the lungs through the pulmonary vein, and re-enters the heart in the left atrium.

Unit 1| Section 1| Structure and function of blood vessels

There are three major category of blood vessel; arteries, veins and capillaries.

Unit 1| Section 1| Arteries

Carry blood under high pressure.

Thicker walls.

More elastic.

More smooth muscle.

Small arteries called arterioles help control blood flow in to the tissues.

Unit 1| Section 1| Veins

Carry blood under low pressure.

Thinner walls.

Less elastic.

Less smooth muscle.

Non-return valves.

Small vessels called venules carry blood from the tissues in to the veins.

Unit 1| Section 1| Capillaries

Smallest and most numerous blood vessels.

Thin walls allow efficient exchange of materials.

Unit 1| Section 1| Structure and function of blood vessels

Arteries are adapted to cope with blood under relatively high pressure and do not need non-

return valves; the pressure alone is enough. Veins carry blood on the return journey back to

the heart, when the pressure is relatively low. Capillaries are found in almost every tissue in

the body, and have the thinnest walls of any blood vessel. This allows for the efficient

exchange of materials.

Unit 1| Section 1| Blood pressure

We’ve talked already about the how blood vessels are adapted to cope with the demands

placed on them by differing pressures, and most people will be familiar with having their

blood pressure taken by a doctor. In this context, blood pressure is ‘a measure of the force

that the blood applies to the walls of the arteries as it flows through them.’

This reading consists of two numbers; one represents the pressure while the heart is

contracting (or ‘beating’) and the other while it is relaxing. These are referred to as systolic

and diastolic blood pressure and the standard units of measurement are millimetres of

mercury.

Unit 1| Section 1| Blood pressure classifications

Blood pressure measurement can be used to determine an individuals’ level of risk of

experiencing certain cardiovascular conditions such as cardiovascular disease (CHD) or

stroke. Average resting blood pressure is 120/ 80 mmHG (millimetres of mercury).

Individuals with blood pressure over 144/94 should be encouraged to see their doctor prior

to beginning physical activity programmes.

Unit 1| Section 1| Circulatory system – summary

We’ve seen that the circulatory system is divided into three parts: the blood, the heart and

the blood vessels. Blood vessels are the transport system for the blood from the heart to the

rest of the body and back again, and although they’re divided into different categories, it’s

important to remember that they’re all linked in a continuous loop.

We’ve also looked at the measure of the force that the blood applies to the walls of the

arteries as it flows through them. This is blood pressure. And you should now be able to

recognise the systolic and diastolic blood pressure classifications.

Unit 1| Section 2| The structure and function of the respiratory system

Structure and function of the respiratory system.

Passage of air through the respiratory tract.

Main muscles involved in breathing.

Process of gaseous exchange of oxygen and carbon dioxide.

Unit 1| Section 2| Structure of the respiratory system

Air is breathed in via the mouth and nose , through the following structures:

Pharynx – the region at the back of the throat where the passages of the nose and

mouth meet, and above where the digestive and respiratory passages separate.

Larynx – the respiratory structure responsible for speech.

Trachea – a rigid tube supported by cartilaginous rings. Diameter is controlled by

smooth muscle action.

Bronchi – branch from the trachea into the left and right lungs. Share similar

cartilaginous and smooth muscle properties to the trachea.

Bronchioles – narrow passages (< 1.0mm) that carry air from the bronchi in to the

alveoli of the lungs.

Unit 1| Section 2| The alveoli

Alveoli are small air sacs with thin walls covered by a network of tiny capillaries. They are

the site at which atmospheric oxygen is exchanged for carbon dioxide (a waste product)

contained in the blood.

Unit 1| Section 2| Gas exchange in the alveoli

Diffusion is the movement of molecules from an area of high concentration to an area of low

concentration. Within biological organisms this usually involves movement across a cell

membrane, such as the walls of the alveoli. Oxygen diffuses from the inhaled air into the

relatively deoxygenated blood, which has been pumped to the lungs from the right hand side

of the heart. In contrast, blood entering the lungs carries carbon dioxide, a waste product of

aerobic energy production. As inhaled air contains little or no carbon dioxide, the gas will

tend to diffuse out of the bloodstream and into the alveoli, before being exhaled.

Unit 1| Section 2| Respiratory musculature and mechanics

During inhalation, the chest cavity expands; the resulting drop in internal pressure forces

atmospheric air in and the lungs inflate. Expansion of the chest cavity is primarily achieved

through the action of the intercostal muscles and the diaphragm.

Unit 1| Section 2| Respiratory musculature and mechanics

The intercostals muscles lift the costal bones (ribs) causing an increase in the volume of the

rib cage. As the diaphragm contracts, it flattens causing a further increase in the volume of

the chest cavity.

Unit 1| Section 2| Respiratory mechanics

Starting with inhalation, the diaphragm contracts, forcing it to flatten downwards, while the

intercostals muscles lift up the rib cage. This causes the volume of the rib cage to increase,

which lowers the internal air pressure, which in turn forces surrounding air into the lungs.

Then, to start exhalation the diaphragm relaxes, moving it upwards while the intercostals

also relax, lowering the rib cage. This decreases the volume of the rib cage and air is forced

out of the lungs again.

Unit 1| Section 2| Respiratory system – summary

The main functions of the respiratory system are the intake of oxygen into the body and the

removal of carbon dioxide from the body.

We’ve seen how air enters the body and how muscles are involved in breathing. And you

should now be able to describe how oxygen passes into the blood while at the same time

carbon dioxide passes back into the lungs to be exhaled. Remember, this process is called

gaseous exchange.

Unit 1| Section 3| Introducing the skeletal system

In this section we will be investigating the skeletal system, the bones and joints of the body

and how they play an integral role in human movement and function.

The skeletal system consists of a number of different materials including bone, cartilage and

ligaments. We will begin by reviewing the various functions that the skeleton provides, the

names of the major bones, the different structures contained within the divisions known as

the axial and appendicular skeleton and the different classifications of bone.

Looking a little deeper inside the bone’s outer surface we will learn about the internal

structure of a long bone and how this solid substance grows and develops. Then finally, we

will take a look at how the spine is constructed; its five distinct divisions and the various

shapes and bends that can develop within both normal and abnormal spinal positioning.

Unit 1| Section 3| Functions of the skeleton

First and foremost the skeleton serves as a rigid, bony framework for the rest of the other

tissues, organs and structures to connect and be anchored to.

Certain areas of the skeleton provide protection to the vital organs. The ribs protect the heart

and lungs, the pelvis protects our reproductive anatomy and the cranium encases the brain.

The longer bones serve as a system of levers that create movement and locomotion. The

muscles, which are anchored to the bones, help generate the forces needed to move the

bones that provide this movement. At the centre of the bones, within the marrow, the body

produces both red and white blood cells. Last, but not least the bones themselves are

composed of a number of different minerals and serve as a storage site, especially for

calcium.

Unit 1| Section 3| Bone anatomy

Starting at the top we have the pelvis, followed by the femur, then the patella at the knee

joint. The tibia is slightly higher up the leg than the fibula, as it forms part of the knee joint

where the fibula doesn’t. The tarsals are in the ankle. The metatarsals make up the rest of

the foot and the phalanges form the toes.

Unit 1| Section 3| Skeletal divisions

It is useful to break the skeleton down into its two major divisions, known as the axial and the

appendicular skeleton.

The axial skeleton forms the central barrel that the limbs are attached to. And it’s the skull,

spine and ribs that make up this central structure. The axial skeleton doesn’t provide much in

the way of movement, but the spine itself does allow for a limited amount.

The appendicular skeleton includes all other segments or appendages that hang off the

central barrel and provide the majority of motion involved in locomotion. This includes the

pelvis, legs and feet, as well as the shoulder girdle, arms and hands.

A useful comparison to remember that an axle is the central rod that anchors the wheels on

a car, just like the axial skeleton serves as the anchor for the moving limbs.

Unit 1| Section 3| Axial or appendicular skeleton?

Axial Skeleton: Ribs; Thoracic vertebrae; Cranium; Coccyx

Appendicular Skeleton: Radius; Metatarsals; Clavicle; Ischium

There are a couple of tricky ones here. The Coccyx sits at the bottom of the spinal column

and is classed within the axial skeleton. But the Ischium, the lower part of the pelvis, is in the

appendicular skeleton, along with the clavicle, radius and the metatarsals.

Unit 1| Section 3| Bone classification

Classification

Description Examples

Long bones Long bones have a greater length than width and consist of a shaft with normally two extremities. They contain mostly compact bone in their diaphysis and more cancellous bone in their epiphysis. (and principally act as levers).

Humerus, femur, fibula, tibia, ulna, radius, metacarpals, metatarsals, phalanges

Short bones Short bones are normally about as long as they are wide. They are usually highly cancellous, which gives them strength with reduced weight.

Carpals and tarsals

Flat bones Flat bones are thin cancellous bone sandwiched between two compact layers. They provide protection and large areas for muscle attachment.

Scapula, cranial bones, costals (ribs), sternum and ilium

Irregular Irregular bones form very complex shapes and therefore cannot be classified within the previous groups.

Vertebrae and calcaneus

Sesamoid (‘seed-like’)

Sesamoid bones develop within particular tendons at a site of considerable friction or tension. They serve to improve leverage and protect the joint from damage.

Patella (kneecap)

Unit 1| Section 3| Bone structure and category

The carpals in the wrist and tarsals in the feet are a similar width and length. The patella is a

sesamoid bone, as it is encapsulated by tendons. The phalanges in the fingers and toes are

small, but in terms of their shape they are longer than they are wide and so are long bones.

The vertebrae of the spine are a more complex shape and fall into the irregular bone

category.

Unit 1| Section 3| Long bone structure

Hyaline cartilage – a thin layer of this smooth, tough connective tissue covers the ends of

long bones at the meeting points between adjoining bones. The cartilage prevents wear and

tear on the bone and allows for smooth motion at the joint.

Epiphysis – the expanded portion at the end of each bone that allows for a larger

articulating surface area to help spread out the forces experienced at the joint.

Diaphysis – the narrower, strong shaft of bone that connects the two ends and houses the

medullary cavity.

Cancellous bone – the porous bone that is found within the epiphyses that provides an

element of elastic strength to the bone.

Epiphyseal growth plate – a narrow band of bony tissue that is the site of rapid bone

growth during childhood. It is largely dormant in adulthood when full bone length has already

been reached.

Compact bone – the dense bony tissue that forms the outermost surface of bones and

gives the diaphysis its strength despite its narrow structure.

Periosteum – a tough, fibrous outer membrane that covers the whole surface of the bone

and provides a strong bonding layer for connective tissues, like ligaments and tendons.

Medullary cavity – the cavity within the shaft of the long bone that contains blood vessels

and bone marrow. The marrow is the site of blood cell formation in the body.

Unit 1| Section 3| Bone growth

Bone growth is known as ossification.

Osteoclasts – clear bone away.

Osteoblasts – build bone.

Factors that affect ossification include:

Nutrition.

Exposure to sunlight.

Hormonal secretions.

Physical activity.

Unit 1| Section 3| Curves of the spine

The spine is composed of five distinct sections, the ‘cervical’ in the neck that supports the

skull, the ‘thoracic’ which is attached to the ribs, the ‘lumbar’ between the ribs and pelvis, the

‘sacrum’ which creates joints with the pelvis, and finally the ‘coccyx’ which is considered to

be our residual tailbone.

The spine is composed of 33 vertebrae, though 9 are fused towards the base and don’t allow

for any motion. This leaves 24 moveable vertebrae.

The cervical region has 7 vertebrae, the thoracic has 12 and the lumbar has 5.

In general terms, the vertebrae are smallest at the top of the vertebral column beneath the

skull and increase in size moving down the spine to the 5th lumbar vertebrae at the base.

The fused, immobile vertebrae make up the remaining sections, 5 within the sacrum and 4

within the coccyx. They form a strong, sturdy base that’s able to transfer forces between the

upper and lower body.

As a general rule the smaller, uppermost vertebrae have the greatest range of motion

through flexion, extension, lateral flexion and rotation, with less in the thoracic and less again

in the lumbar.

The lumbar vertebrae support the most bodyweight and so they have the greatest role in

stability and strength, hence their larger size and more limited range of movement.

Unit 1| Section 3| Postural deviations

Neutral spine

A neutral spine is the term used to describe a slight backward curve or arch in the lower

back and a slight forward curve in the mid back. This position, which will vary from one

individual to the next, seems to be the ideal position to decrease stress on passive

structures of the body, such as the vertebrae and ligaments. This is therefore an ideal

postural position to teach those participating in physical activity to help reduce the risks of

lower back pain. Lifting in this neutral spine will help spare the stress on passive structures

and teach the abdominal and hip musculature to hold the body in this optimal position.

Common postural abnormalities

• lordosis (excessive lower back curvature)

• kyphosis (excessive mid-back curvature)

• scoliosis (a lateral deviation of the spine)

These abnormalities increase stress on the spine and surrounding soft tissue structures, as

well as decreasing the efficiency with which the body moves.

Unit 1| Section 3| Spinal anatomy

The cervical take least load and are the smallest vertebrae. The thoracic curve is forward

encouraging flexion. The lumbar curve is backward encouraging extension. The sacrum

forms a solid base between spine and pelvis

Unit 1| Section 3| Skeleton structure and function – summary

The skeletal system consists of a number of different materials including bone, cartilage and

ligaments. We have now explored the various functions of the skeleton, the major bones, the

different structures in the axial and appendicular skeleton and the different classifications of

bone.

We have also taken the example of a long bone to look in detail at its internal structure.

Then, finally, we studied the construction of the spine and its five divisions, along with the

different shapes and bends that can develop within it.

Unit 1| Section 4 | Introduction to joints

A joint can be defined as the junction of two or more bones. There are three main types of

joint in the body and these are classified according to their degree of movement. Fibrous

joints occur where there are immovable and interlocking bones, such as the plates of the

skull.

In contrast, cartilaginous joints are slightly movable joints brought together by ligaments, like

the joints between the vertebrae of the spine. We should appreciate that the movement

available at these joints is necessary in the role that they perform. Without this small amount

of movement in the spine it would be rigid and unable to perform its various required

functions.

Finally, there are synovial joints. These are freely movable and therefore situated at the

points in our body where a lot of movement is necessary; like our shoulders, elbows, knees

and ankles.

Unit 1| Section 4 | Synovial joint structure

Synovial joints are the most common type of joint in the body, but they all have some

common characteristics. The ends of the bones that form a synovial joint are covered by a

layer of hyaline cartilage. Hyaline (or articular) cartilage provides protection and cushioning

to the bone ends. If you can picture the bone ends of your Sunday roast pork joint, and the

blue-ish white, tough covering of those bone ends you will start to appreciate the

appearance, structure and function of hyaline cartilage.

All synovial joints are stabilised and supported by ligaments. Ligaments connect bone to

bone across a joint. They will allow the normal range of movement at a joint but exist to

prevent any unwanted movement that could damage the joint.

Finally, synovial joints are surrounded by a fibrous capsule. This capsule is lined by a

synovial membrane which secretes synovial fluid. Synovial fluid has an appearance and

texture similar to egg white and, like the oil in a car engine, acts to lubricate the joint and

allow for smooth movement.

Unit 1| Section 4 | Types of synovial joint

There are six types of synovial joint in the body: ball and socket joint, saddle joint and sliding

joint, which we have here, plus hinge, pivot and ellipsoid joints. The different structures of a

synovial joint determine the movements available. Next we’ll explore the detail of each one.

Unit 1| Section 4 | Synovial ball and socket joints

Examples of a ball and socket joint:

Shoulder joint, formed by the humerus meeting the scapula.

Hip joint, formed by the femur meeting with the pelvis.

The shallower socket in the shoulder allows for greater range at the expense of stability.

The deeper socket at the hip provides greater stability, but has less range than the shoulder.

Unit 1| Section 4 | Synovial hinge joints

Allow simple bending, called flexion and extension.

Elbow joint: formed by the meeting of the humerus and ulna.

Knee joint: formed by the meeting of the femur and the tibia.

Unit 1| Section 4 | Synovial pivot joints

Atlas: axis joint in the neck allows the head to turn and rotate.

Humerus and radius: allow the forearm to twist and turn the hand over.

Unit 1| Section 4 | Synovial saddle joint

Carpometacarpal joint at the base of the thumb.

Allows for flexion, extension, abduction and adduction, but prevents rotation.

Unit 1| Section 4 | Gliding and ellipsoid joints

Gliding joint:

The acromioclavicular joint is formed by the meeting of the acromion (scapula) and

the clavicle.

Mid-carpal joint in the wrist.

Mid-tarsal joint in the foot.

Ellipsoid joint:

The metacarpophalangeal joint is formed by the meeting of the metacarpals in the

hand and the first phalanges in the fingers.

They allow for flexion, extension, abduction and adduction.

Unit 1| Section 4 | Identifying types of synovial joint

The hip and shoulder are ball and socket joints. An example of a hinge joint is the elbow.

Pivots are found in the uppermost cervical vertebrae of the neck and between the humerus

and radius. An example would be the metacarpophalangeal joint at the thumb.

Unit 1| Section 4 | Joint movement

Flexion: The angle of the joint decreases or the return from extension.

Extension: The angle of the joint increases or the return from flexion.

Rotation: A bone spinning within the long axis of the joint – may be internal or external.

Abduction: Moving outwards away from the midline of the body.

Adduction: Moving inwards toward the midline of the body.

Unit 1| Section 4 | Joint movement

Flexion is the joint angle becoming smaller. It’s not abduction because that’s where the limb

is moved sideways, away from the body’s midline.

Unit 1| Section 4 | Joint movement

Adduction describes the leg being moved closer to the midline of the body.

Unit 1| Section 4 | Specific joint movements of the shoulders and hips

Horizontal flexion: Arm towards the midline of the body in the horizontal plane.

Horizontal extension: Arm away from the midline of the body in the horizontal plane.

Circumduction: A circular or cone-shaped movement available at ball and socket

joints.

Elevation: Upward movement of the shoulder girdle.

Depression: Downward movement of the shoulder girdle.

Protraction: Forward movement of the shoulder girdle.

Retraction: Backward movement of the shoulder girdle.

Lateral flexion: Spine bending to the side.

Unit 1| Section 4 | Specific joint movements of the shoulders and hips

Horizontal flexion is a movement unique to the shoulder joint. The arm moves towards the

midline of the body in the horizontal plane.

Unit 1| Section 4 | Specific joint movements of the shoulders and hips

Elevation is another movement unique to the shoulder joint, and involves upward movement

of the shoulder girdle.

Unit 1| Section 4 | Specific joint movements of the hands and feet

Pronation: Turning the palm of the hand to face downward.

Supination: Turning the palm of the hand to face upward.

Dorsiflexion: Angle between the foot and the tibia decreases.

Plantarflexion: Angle between the foot and the tibia increases.

Inversion: Sole of the foot turns to face the midline.

Eversion: Sole of the foot turns to face away from the midline.

Unit 1| Section 4 | Specific joint movements of the hands and feet

Inversion is one of the four unique movements available at the ankle. Inversion is the

movement of the foot so that the sole is turned to face inwards, towards the midline of the

body.

Unit 1| Section 4 | Specific joint movements of the hands and feet

Plantarflexion is where the angle between the foot and tibia increases and the toes are

pushed downwards to the ground, like going on ‘tip-toes’.

Unit 1| Section 4 | Identifying joint movement

Extension: Examples would include hip and shoulder extension.

Abduction: Examples would include shoulder and hip abduction.

Lateral flexion: This movement would occur at the spine.

Inversion: This movement would occur at the ankle.

Unit 1| Section 4 | Specific joint movement

Protraction and depression: Scapula motion over ribs allows forward (protraction) and

downward (depression).

Circumduction and extension: Only ball and socket joints can circumduct.

Inversion and dorsiflexion: Sole of foot moving inwards (inversion). Toes towards tibia

(dorsiflexion).

Flexion and supination: The elbow flexes, but also supinates the hand by the joint formed by

the humerus and radius.

Unit 1| Section 4 | Joints – summary

Remember that a joint is the junction of two or more bones, and there are three main types

in the body; fibrous joints which are immovable, cartilaginous joints which are slightly

moveable and synovial joints which are freely moveable.

To develop a thorough understanding of the effects of exercise it’s important to know the

effect that muscles have on the various joints of the body. And, so, we have explored the

lists of terms that are required to get a full understanding of joint movement.

Unit 1| Section 5| The muscular system

We’ve seen that the skeletal system is connected by a series of joints and the each of these

joints enables particular movements.

In this section we’ll explore how muscles generate the forces necessary to create and

control movement. We’ll look at all the muscles in the body, the basic structure of skeletal

muscle, the three types of muscle fibre and the muscle actions at each joint.

Unit 1| Section 5| Characteristics of muscle

Contractility: the ability to shorten and generate force.

Extensibility: the ability to stretch.

Elasticity: the ability to recoil following a stretch.

Excitability: the ability to respond to electrical stimuli.

Unit 1| Section 5| Types of muscle tissue

Smooth muscle is involuntary and is the most diverse form of muscle found in the body. It is

typically found in hollow tubular organs such as the intestines, airways and circulatory

system. It allows the intestines to push food along the gut (peristalsis) and helps control

blood flow throughout the circulatory system.

Cardiac muscle is involuntary and located only in the heart. It is capable of contracting

without input from elsewhere (autorythmicity), however the rate of contraction (i.e. beats per

minute) is moderated by the nervous and endocrine (hormonal) systems.

Skeletal muscle is predominantly under-voluntary control, although it is heavily influenced by

involuntary reflexes. It exerts force on the skeletal system via tendons and helps generate

and control movement.

Unit 1| Section 5| Skeletal muscle structure

Skeletal muscle is fibrous in nature and involves the interaction of the following structures:

1. Bone – skeletal muscles are attached to the fibrous outer coating (periosteum) of

bone via tendons.

2. Tendon – the link between muscle and bone, they enable contractile forces to be

transferred across the joints of the skeleton. In contrast to muscle, they are inelastic and

relatively poorly perfused with blood.

3. Muscle belly – the area of muscle containing all the force-generating fibres.

4. Epimysium – connective tissue which encloses the muscle belly.

5. Fasciculi – formed by bundles of muscle fibres.

6. Perimysium – connective tissue surrounding the fascicule.

7. Muscle fibre – long tubular cells containing myofibrils.

8. Endomysium – connective tissue surrounding the muscle fibres.

9. Myofibrils – composed of the contractile proteins actin and myosin.

Unit 1| Section 5| Actin and myosin – the contractile proteins

The myofibrils contain two proteins; actin and myosin. Small protrusions on the myosin

filament attach themselves to the actin and rotate, creating a pulling action and causing the

two filaments to try to slide over each other. The process is replicated along the length of the

myofibril and throughout the entire muscle fibre. This causes the muscle to contract.

Unit 1| Section 5| Types of skeletal muscle fibre

Slow twitch (or Type I) fibres.

Fast twitch (or Type II b) fibres.

Intermediate (or Type II a) fibres.

Unit 1| Section 5| Slow twitch muscle

Relatively small diameter.

Well supplied with blood.

More mitochondria.

Low force generation.

Slow to fatigue.

Unit 1| Section 5| Fast twitch muscle

Relatively large diameter.

Relatively poor blood supply.

Fewer mitochondria.

High force generation.

Quick to fatigue.

Unit 1| Section 5| Intermediate muscle fibres

Fast and slow twitch fibres cannot easily be converted from one to the other. Intermediate

muscle fibres can change characteristics to reflect the predominating exercise activities.

Unit 1| Section 5| Muscle fibre type and exercise

It is worth highlighting that different intensities and durations of physical activity only

emphasise different muscle fibre types. For example, slow twitch muscle fibres will still be

used in even the most explosive of movements.

Unit 1| Section 5| Anterior musculature and muscle actions

Bicep brachii: an upper arm muscle responsible for elbow flexion and supination and

shoulder flexion.

Deltoid: covering much of the shoulder, with anterior, lateral and posterior portions.

Anterior and lateral parts enable flexion, horizontal flexion, internal rotation and abduction

of the shoulder.

Pectoralis major: located across the chest, causes adduction, horizontal flexion, internal

rotation and flexion of the shoulder.

Serratus anterior and pectoralis minor: run from the ribs to the scapula. Stabilise the

shoulder girdle during shoulder activity. Cause protraction and depression of the shoulder

girdle.

Obliques (internal and external): wraps around the waist from the ribs to the middle of the

abdomen. Causes rotation and lateral flexion of the spine.

Rectus abdominis: run vertically up the front of the abdomen. Causes flexion and lateral

flexion of the spine.

Quadriceps: comprises four muscles and located at the front of the thigh. Enables

extension of the knee and flexion of the hip.

Hip adductors: muscles which occupy the inner thigh. Enable adduction of the hip.

Tibialis anterior: located between the tibia and fibula to the front of the shin. Responsible

for dorsiflexion and inversion of the ankle.

Unit 1| Section 5| Posterior musculature and muscle actions

Triceps brachii: located the rear of the arm. Enables extension of the elbow and extension of

the shoulder.

Posterior deltoids: sited at to the rear of the shoulder. Causes extension, external rotation

and horizontal extension of the shoulder.

Trapezius: divided in to upper, middle and lower portions and located across the neck and

upper back. Allows elevation, retraction and depression of the shoulder girdle. Can also

facilitate head and neck movement.

Latissimus dorsi: the largest muscle of the back. Runs from the sacrum to the middle of the

chest and attaches to the front of the upper arm. Causes extension, adduction and medial

rotation of the shoulder.

Erector spinae: a thick group of muscles running either side of the length of the spine. Helps

maintain an upright posture and allows extension and lateral flexion of the spine.

Hip abductors (gluteals): located on the outer thigh. Cause abduction of the hip.

Gluteus maximus: the most superficial and posterior of the gluteals. Allows extension,

external rotation and abduction of the hip.

Hamstrings: three muscles running from the ichium of the pelvis through to the rear of the

lower leg behind the knee. Enables extension of the hip and flexion of the knee.

Gastrocnemius: a posterior calf muscle running from the back of the femur to the heel.

Assists with knee flexion and is a powerful plantar flexor.

Soleus: a broad posterior calf muscle beneath the gastrocnemius. Attaches from the upper

rear of the tibia to the heel (via the same tendon as the gastrocnemius). Enables body

plantar flexion.

Unit 1| Section 5| Core musculature

Transversus abdominis (TVA).

Multidifidus.

Diaphragm.

Pelvic floor.

These muscles squeeze the viscera causing rise in intra abdominal pressure, providing

stability to the trunk, particularly during exertion.

Unit 1| Section 5| Identifying the core musculature

Transversus abdominis (TVA): located beneath the obliques and running like a corset

from the lumbar region through to the middle of the abdomen. It compresses the viscera

and increases intra-abdominal pressure.

Diaphragm: when activated it applies downward pressure to the viscera. As the

diaphragm is one of the primary respiratory muscles, activities that challenge the core

will result in changes in breathing patterns.

Multifidus: a series of small muscles running the length of the spine from the sacrum to

the neck. In particular provides trunk stability during spinal extension and rotation.

Pelvic floor: comprises a group of small muscles forming a sling-like structure from the

coccyx to the pubis. Provide support for the bladder and intestines, particularly during

straining activities. Weakness in the pelvic floor can lead to urinary incontinence and

compromise core stability.

Unit 1| Section 5| Types of muscle action

Concentric: muscle generates force and shortens (lifting or accelerating).

Eccentric: muscle generates force and lengthens (lowering and decelerating).

Isometric: muscle generates force and stays the same length (holding/ static control).

Unit 1| Section 5| Types of muscle action

Concentric: Getting out of a chair; Pulling yourself out of a swimming pool.

Eccentric: Walking down stairs; Lowering a bucket into a well.

Isometric: Holding your breath; Holding open a door.

Unit 1| Section 5| Muscular system – summary

We’ve seen that muscles work to create forces across joints and cause movement, and that

there are three types of specialised muscle tissue: smooth muscle, cardiac muscle and

skeletal muscle.

We’ve also run through the names and locations of the anterior and posterior skeletal

muscles. And we’ve taken a closer look at the basic structure of skeletal muscle.

Most skeletal muscles are a mix of fibre types and we’ve explored slow and fast twitch fibres

and how they relate to different types of activity and exercise.

Finally we looked at concentric, eccentric and isometric muscle actions and how they relate

to different human movements.

Unit 1| Section 6| Musculoskeletal system life course

Young people (14-16).

Prenatal and postnatal women.

Older people (50+).

Unit 1| Section 6| Life course of the musculoskeletal system – young people

Young people aged 14-16 are likely to experience significant physiological and anatomical

changes associated with puberty. These include a growth in skeletal and muscle tissue as

well as a change in body composition.

During this period, skeletal growth plates can be vulnerable to fracture, so care should be

taken to moderate the load, impact and volume of exercise activities.

In this phase of the skeletal life course it’s better to focus on building skills than muscle or

fitness.

Unit 1| Section 6| Prenatal and postnatal women

A healthy lifestyle should be adopted by an expecting mother, which includes exercising. But

exercise should be performed with as little impact as possible, and both pre and postnatal

women should exercise their pelvic floor.

Unit 1| Section 6| Life course of the musculoskeletal system – prenatal and postnatal

women

During pregnancy, changes in weight and the body’s centre of gravity can make exercise

challenging. So it makes sense to select exercise activities that lessen or remove impact.

In the second trimester of pregnancy, a hormone called relaxin is released, softening the

ligaments and cartilage around the pelvis to help the delivery of the baby. Its effects are not

confined to the pelvis, so care should be taken to avoid excessive or vigorous stretching.

Relaxin levels may remain high in the postnatal period, and tend to remain so for longer if

the woman is breastfeeding.

Particular attention should be paid to the pelvic floor musculature, which may have been

weakened by the pregnancy and birth. So, pelvic floor exercises should be encouraged in

both the pre and postnatal periods.

Unit 1| Section 6| Life course of the musculoskeletal system – older exercisers

As we get older, a number of age-related changes occur, which have important implications

for our ability to exercise. It gets harder to sustain muscle mass; leading to a loss of strength.

Bone density may also decline and in some cases this leads to bones becoming brittle and

vulnerable to fracture.

Older exercisers should be encouraged to perform regular weight-bearing activity to retain

muscular strength and bone density. Exercises that improve balance and coordination are

also important because older people are more vulnerable to trips and falls.

Unit 1| Section 6| Exercise and special populations

14-16 year olds are vulnerable to growth plate injury. Pre/ postnatal women have weakened

pelvic floor and joint instability due to the effects of relaxin. Older exercisers have lower

bone density and lower strength often coupled with poor balance and reactions.

Unit 1| Section 6| Musculoskeletal system life course – summary

Remember that during puberty an increase in hormone production results in an increase in

muscle mass, while at the other end of the scale, a large percentage of the elderly find

difficulty in simply standing from a seated position due to a decline in muscle functioning.

It is important that we understand the changes that the musculoskeletal system undergoes

as a result of the ageing process and also pregnancy.

You should now have a basic appreciation of these changes and a better understanding of

the implications they have on exercise for young people in the 14-16 age group, pre and

postnatal women and older adults aged over 50.

Unit 1| Section 7| Energy systems

We have to look deep within cellular physiology to understand how we produce energy to

help the body complete all its important and vital functions.

The cells of our body have developed a number of different methods for drawing out the

energy from our food, converting it to a useable form within the body, and utilising it in the

cells or, if it’s not currently needed, storing it nearby for later use.

These various mechanisms are pretty complex and university courses spend hours of study

explaining and teaching the biochemistry involved. Fortunately, we don’t need to work

through these concepts at the same minute level of detail.

We’ll be reviewing how we use carbohydrates, fats and proteins to create a substance called

ATP, as well as learning about the three different energy pathways that help provide energy

for the body.

Unit 1| Section 7| Adenosine triphosphate (ATP)

Our bodies require energy to power locomotion or movement, generate heat and grow or

repair tissue. This energy comes from a substance known as adenosine triphosphate (ATP).

ATP is the only fuel the human body recognises and uses. Food and certain drinks we ingest

provide us with energy, such as carbohydrate, fat and protein with which to rebuild our very

limited stores of ATP when they have been used up.

ATP is composed of one adenine molecule bound with three phosphate molecules. ATP

releases its energy when one of its high energy bonds is broken, and it is converted to

adenosine diphosphate (ADP). When this high energy bond is broken down, energy is

released. There is a very limited store of ATP within the muscles and this will only last for

approximately one-two seconds.

Unit 1| Section 7| The aerobic energy system

The aerobic system produces energy slowly. It produces water and carbon dioxide as well

as ATP. It uses inhaled oxygen, and can produce energy for a relatively long period of time.

Unit 1| Section 7| The aerobic energy system

Oxygen dependency: Aerobic

Speed of energy production: Slow

Substrate needed (energy source): Glycogen and fat

Amount of energy produced: Unlimited ATP

By-products of energy production: No fatiguing waste products (only CO2 and H2O)

Duration of energy production: Long duration

Intensity of activity: Low intensity (up to 60% max effort)

Recovery required: Time to eat and drink: (to replenish fuel stores)

Predominant fibre type: Type I

Unit 1| Section 7| The lactate energy system

The lactate energy system produces energy moderately quickly. It doesn’t produce water or

CO2, its main by-product is lactic acid. It doesn’t use inhaled oxygen, and can only produce

energy for a relatively short period of time.

Unit 1| Section 7| The lactate energy system

Oxygen dependency: Anaerobic

Speed of energy production: Rapid

Substrate needed (energy source): Glycogen

Amount of energy produced: Limited ATP

By-products of energy production: Lactic acid

Duration of energy production: 1-3 mins of intense activity

Intensity of activity: High intensity (60-95% max effort)

Recovery required: 20 min-2 hrs: (breakdown lactic acid)

Predominant fibre type: Type II a

Unit 1| Section 7| The creatine phosphate energy system

The creatine phosphate system does, of course, produce energy very quickly. It doesn’t

produce any fatiguing by-products, doesn’t require oxygen and recovers very quickly

compared to the other energy systems.

Unit 1| Section 7| The creatine phosphate energy system

Oxygen dependency: Anaerobic

Speed of energy production: Very rapid

Substrate needed (energy source): Stored chemical energy (phosphocreatine)

Amount of energy produced: Very limited ATP

By-products of energy production: No waste products

Duration of energy production: Short duration (0-10 secs)

Intensity of activity: High intensity: (95-100% max effort)

Recovery required: Quick recovery (30 sec – 5 min)

Predominant fibre type: Type II b

Unit 1| Section 7| Identifying energy systems

The aerobic energy system is dominant when there is enough oxygen in the cell to meet the

energy production requirements. If the production of lactic acid exceeds the muscles and

cardiovascular system’s ability to disperse it, there will be a build up.

The creatine phosphate system is used when there is not enough oxygen (anaerobic), such

as during near maximal exertion when a muscle needs to generate a lot of force quickly.

Unit 1| Section 7| Identifying energy systems

The aerobic energy system is dominant when there is enough oxygen in the cell to meet the

energy production requirements. If the production of lactic acid exceeds the muscles and

cardiovascular system’s ability to disperse it, there will be a build up.

The creatine phosphate system is used when there is not enough oxygen (anaerobic), such

as during near maximal exertion when a muscle needs to generate a lot of force quickly.

Unit 1| Section 7| Energy systems – summary

You should now have a better understanding of how we produce energy to help the body

carry out its essential functions.

We’ve seen how the cells of our body have developed a number of different methods for

drawing out the energy from food and converting it to be used by the body.

We’ve looked at how we use carbohydrates, fats and proteins to create a substance called

ATP, as well as learnt about the aerobic, lactate and creatine phosphate energy systems

that help supply energy for the body.

Unit 1| Section 8| The nervous system

The nervous system is the dominant control system in the human body. It helps to collect

information, interpret that information and then determine and stimulate an appropriate

response if required. Elements of the nervous system are found throughout the whole body;

from the brain right down to the tips of our fingers and toes. It would be an understatement to

say that we simply could not function without it.

Unit 1| Section 8| Roles of the nervous system

The nervous system as a whole has three very clear and distinct roles or functions.

First, it serves as a sensory unit to collect information about the internal and the external

environments. Internal neural monitoring includes things like body temperature, digestion

and heart rate. External monitoring includes vision, sounds and touch.

The second role is that the nervous system must be able to analyse and interpret the

information collected by sensory receptors. There are many daily decisions made by the

nervous system that are beyond our conscious mind, but there are some elements of neural

interpretation that come through learning and education.

The third role is the neural response elicited as a result of analysis and interpretation. The

nervous system has to make sure that the level of response is accurate and appropriate to

the sensory information collected.

In the vast majority of cases these three distinct neural roles blend together seamlessly to

provide a highly efficient control system.

Unit 1| Section 8| Nervous system divisions

The nervous system is divided into two primary categories, the central and the peripheral

nervous systems.

The central nervous system is composed of the brain and the spinal cord. The reason these

two sections are considered the central nervous system is because they are responsible for

receiving and interpreting neural information and eliciting a response; they are the

processors.

The cerebellum in the brain is primarily responsible for coordinating and controlling human

movement.

The remaining nerves are considered the peripheral system. The periphery is composed of

sensory and motor nerves. The sensory nerves collect information about the environment

and send the signal into the central nervous system for processing.

The motor nerves send signals from the central nervous system out to the effector muscle,

organ or tissue to bring about the required response. Both divisions are essential for good

neural functioning and in monitoring and controlling human movement.

Unit 1| Section 8| Identifying nervous system roles

Sensation: Sensory neurons gather information and send it into the CNS.

Analysis: The CNS interprets sensory information and elicits a response.

Response: The CNS stimulates the motor neurons to create a desired action.

Unit 1| Section 8| Muscular contraction

The sliding filament theory of muscular contraction was first devised in the 1950s and has

become widely accepted as the most popular model of muscle function. The nerves of the

body stimulate the muscle at the level of the muscle fibre. Contained within each muscle

fibre are smaller myofibrils and along the length of each myofibril are a series of small

working units called sarcomeres. Contained within each sarcomere are thick and thin protein

filaments. The thick filament, myosin, and the thin filament, actin, do not reduce in length

during contraction but slide over one another as myosin pulls the actin fibres inwards. The

cumulative effect of all the sliding filaments in all the sarcomeres in all the myofibrils within

the muscle fibre brings about a contraction and a shortening of that muscle fibre. When the

nerve associated with a muscle fibre fires, it stimulates all the sarcomeres within the fibre to

switch on and contract.

Unit 1| Section 8| Motor unit recruitment

A motor unit is simply a nerve and the muscle fibres it innervates (supplies). The size of a

motor unit can vary from a single nerve stimulating only ten muscle fibres up to much larger

motor units where a single nerve may stimulate as many as a thousand muscle fibres.

Larger motor units are found in muscles that are required to generate greater levels of force

and smaller motor units in muscles responsible for lesser force and finer control of

movement.

The ‘all or nothing law’ states that when a nerve in a motor unit is stimulated then all of the

muscle fibres connected to that nerve will be stimulated to contract.

There is no partial level of contraction in a motor unit, it is either switched on and all the

muscle fibres contract or it is switched off and none contract.

But muscles are capable of grading the amount of force they generate. This is achieved

through varied recruitment of the number of motor units. For example, if the muscle has a

motor unit size of 1 nerve to 50 muscle fibres and we needed to create a single unit of force

then stimulating a single motor unit would be sufficient.

However, if 6 times that force was required then the nervous system would stimulate 6 motor

units, which would activate 300 muscle fibres to deliver the correct amount of force.

Unit 1| Section 8| Neuromuscular contraction

In a reflex reaction the nervous system detects the risk of heat damage and sends a rapid

signal to the central nervous system; in this case the spinal cord. The analysis of the

message creates a rapid response via the motor nerves. The muscle fibres in the motor

units are stimulated to contract which quickly raises the hand away from the hot object.

Unit 1| Section 8| Identifying motor unit recruitment

An increase in force is created by stimulating more motor units and a lesser degree of force

is created by firing fewer motor units.

Unit 1| Section 8| Nervous system and exercise

Exercise has positive effects on the nervous system:

Development of stronger neural links and movement patterns and programmes in the

brain.

Improved sensory feedback from joint and muscle receptors.

Better movement purity and reduced faulty movements.

Cardiovascular training primarily develops Type 1 motor units causing:

Asynchronous motor unit firing for sustained muscular performance.

Increased size and number of mitochondria.

Increased oxygen delivery to the muscle fibres.

Increased aerobic enzymes function within the muscle tissue.

Improved aerobic threshold and ability to function without lactic acid build-up.

Resistance training primarily develops Type 2 motor units causing:

Decreased neural inhibition to allow better motor unit recruitment.

Increased thickness or diameter of the recruited muscle fibres.

Increased force production capacity of the muscle fibres.

Increased anaerobic threshold and resistance to fatigue when lactic acid is present.

Unit 1| Section 8| Identifying the effects of exercise on the nervous system

Cardiovascular training primarily develops Type I motor units causing increased oxygen

delivery to the muscle fibres. Resistance training primarily develops Type II motor units

causing increased force production capacity of the muscle fibres.

Unit 1| Section 8| Nervous system – summary

You should now know that the nervous system has two main divisions: the central nervous

system, which is the brain and spinal cord, and the peripheral nervous system, which is all

the branches of nerves that lie outside the spinal cord.

We’ve also looked at motor units and muscle fibre recruitment. Remember that a motor unit

is a single motor neuron and all the muscle fibres that it supplies. It’s typically made up of

one type of muscle fibre, spread throughout the muscle – that’s Type 1, Type 2 A or Type 2

B.

Finally, we explored the changes that occur in the neuromuscular system as a result of

exercise and physical training, which can enhance neuromuscular connections and, in turn,

help to improve motor fitness.