Muscles

(External oblique)

Hamstrings

Quadriceps

Your body has over 600 muscles to

enable it to move.

There are 3 types of muscle:

1. Heart (cardiac) muscle, which is only found in the heart.

2. Involuntary (smooth) muscle, found in places like your iris, intestines, oesophagus.

3. Voluntary (skeletal) muscle, any muscle that you can consciously control.

Cardiac / Heart muscle

Cardiac muscle has a built in ‘pacemaker’, known as the sino-atrial node, that controls the rate of the heartbeat. The rate of heartbeat is an involuntary action but can be influenced by factors such as stress, medication, illness and exercise.

These factors change the amount of hormones which are released, which result in a change of heart rate.

Involuntary (smooth) Muscle

Found in organs, digestive system and blood vessels, these muscles are completely controlled by the autonomic nervous system (spinal cord). Called smooth muscle due to its smooth appearance under a microscope.

Voluntary (skeletal) Muscle

This type of muscle is attached to the skeleton and provides movement and stability. It is also called striated muscle because of its stripey appearance under a microscope. The muscles are controlled by the central nervous system (brain), therefore it requires conscious thought for movement to occur.

Muscle Type Muscle Structure Primary Function Control Mechanism

Location

Cardiac Muscle A combination of striated and smooth muscle tissue

Allows pumping action of the heart, during rest and exercise

The heart’s automatic nervous system assisted by the autonomic nervous system (ANS)

Heart

Involuntary Muscle

Smooth Maintains the different functions of many vital organs of the body

Controlled without conscious thought.ANS

Blood vessels, organs

Skeletal Muscle Striated or striped To provide movement of the body

Central Nervous system (CNS) with conscious thought.

Attached to bones

Muscle Movement

• A tendon is a tough but flexible tissue that connects muscle to bone. It is skeletal muscle that is responsible for movement during sporting activity.

• Muscle can only pull, therefore, during muscular contraction, muscles pull on bone to cause movement.

•To cause movement, muscle tissue contracts. The cells of the muscle use chemical energy to work. This energy is created from the foods we eat. Carbohydrate foods are the main fuel provider for muscle contraction.

Antagonostic Pairs

Muscles work in pairs to provide movement for physical activity.

• Prime mover (agonistic) – This muscle determines the movement of an action via contraction. For example, during a bicep curl, the prime mover during the flexion phase is the biceps.

• Antagonistic – This muscle works together with the prime mover but creates an opposite action. For example during the bicep curl, during the flexion phase the triceps enables the arm to bend at the elbow joint for the bar to move to the shoulder girdle.

Prime Mover (shortens)

Antagonist (lengthens)

Bicep curl flexion

Muscle Contractions

There are 3 main types of muscle contraction occurs. Two where obvious movement occurs and one where there is no obvious movement visible.

Isometric contraction is where the muscle stays the same length during contraction, or when activity is being carried out. Tension occurs in the muscle but the distance between the ends stays the same.

Isotonic Concentric contraction is where the muscle shortens when performing an action. There is obvious movement when the ends of the muscle move closer together.

Isotonic Eccentric contraction is occurs when the muscles lengthen under tension. The ends of the muscle moves further away during an action.

Phase of Play Muscle Group Prime mover Contraction

The lock after the scrum has engaged

QuadricepsHamstringsGastrocnemius

Quadriceps Isometric

The arms after the ball has been thrown in from a lineout

TricepsBiceps

Triceps Isotonic concentric contraction

Isotonic eccentric contraction

The draw back of the leg as it prepares to kick the ball.

HamstringsQuadriceps

Hamstrings Isotonic concentric contraction

Isotonic eccentric contraction

Effects of Exercise on the Muscular SystemShort Term

• An increase in blood flow to the exercising muscles, due to the increased demand of oxygen by these muscles.

• An increase in the demand of fuel by the working muscles to complete the activity.

• An increase in the waste products that are produced by the working muscles resulting in the demand for these waste products (e.g carbon dioxide, lactic acid) to be removed by the body muscles.

• An increase in body temperature due to the muscles working harder to provide movement.

Long Term

• Muscles become bigger and stronger depending on the type of exercise you undertake. It takes up to six weeks for changes to the body to be seen. However, it only takes two weeks for these changes to be lost if exercise does not continue.

The increase in size of muscles through exercise is called

‘hypertrophy’