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THE MUSCULAR SYSTEM
The muscular system involves all the muscles within the human body. There are different types of muscle that all have different jobs and roles. The main types of muscle we have are voluntary, involuntary and cardiac muscle.
TYPES OF MUSCLE
Voluntary Muscle
Also referred to as skeletal muscle, these muscles will continuously contact and relax whilst you consciously make them work (you decide that you want them to produce the movement). When these muscles contract the tendon of the muscle will pull against the skeleton causing movement of the body.
Involuntary Muscle
Also referred to as smooth muscle, these muscles will contract and relax automatically or unconsciously. They will be working 24 hours a day without you thinking about it. These muscles can be found in the digestive system and walls of the blood vessles, they will help with things such as digestion, circulation and respiration.
CARDIAC MUSCLE
These muscles are only found in the walls of the heart. The muscles contract and relax to allow the heart to pump blood around the body. This type of muscle is also an involuntary muscle. Cardiac muscle will never tire or fatigue which is very important to staying alive!
THE MAJOR MUSCLes
FRONT OF THE BODY (ANTERIOR)
REAR OF THE BODY (POSTERIOR)
Types of Muscle Contraction
There are two main types of muscle contraction that skeletal muscles can create; isotonic and isometric contractions.
ISOTONIC CONTRACTION
An isotonic contraction is where the contraction of the muscle, or group of muscles, causes movement to occur. The contracting muscle will shorten and fatten causing the tendon to pull on the bone which will create the movement of that bone or joint.
CONCENTRIC
During a concentric contraction the muscle will contact and shorten to create the movement of the bone or joint. Examples of this will be when a footballer is preparing to kick the ball their hamstring will contract and shorten causing flexion of the knee. Also, when lifting weights and performing a bicep curl, the bicep will contract and shorten causing flexion of the elbow.
ECCENTRIC
During an eccentric contraction the muscle will lengthen to create or control the movement. An example of this will be the quadricep lengthening whilst performing the downward phase of a weighted squat. The quadricep will work with the hamstring muscle (which will be contracting) to ensure the movement is performed efficiently and under control.
ISOMETRIC CONTRACTION
During an isometric contraction the muscles will contract but there will be no movement created. The muscles therefore do not change in size or length. These type of contractions will lead to developments in static strength. Examples of this will be a wall sit or a handstand in gymnastics.
ANTAGONISTIC PAIRS
Muscles in the body sometimes work as pairs. These pairs are known as antagonistic pairs. This is where as one muscle contracts (shortens and fattens), this is known as the agonist, the other muscle will relax (lengthen), this muscle is known as the antagonist.
This can be seen in the arm where the bicep and tricep muscles work together to create movement at the elbow. As the bicep contracts, this will pull on the bones causing the angle at the elbow to decrease. To allow this to happen, at the same time the tricep muscle will be relaxing and lengthen to allow the movement to occur. Other examples of antagonistic pairs are the quadriceps and hampstrings, the hip flexors and the gluteals and the tibialis anterior and the gastrocnemius.
MUSCLE FIBERS
TYPE 1 MUSCLE FIBRES
Type 1 muscle fibres are also referred to as slow twitch muscle fibres. These fibres are red in colour due to the amount of capillaries and mitochondria that are transporting the oxygenated blood and use oxygen more efficiently. They contract more slowly and as a result are able to work for longer periods of time without fatiguing. These fibres are suited to longer duration, lower intensity activities such as long distance running.
TYPE 2 MUSCLE FIBRES
Type 2 fibres can be seperated into two different categories; type 2a and type 2x fibres.
Type 2a
Type 2a fibres are also known as fast oxidative muscle fibres and are a hybrid of type 1 and type 2 fibres.
Type 2x
Type 2x fibres are also known as fast glycolytic muscle fibres. These fibres are more white in colour and have large stores of glycogen and great for short, powerful bursts of movement. They have a fast contraction speed but fatigue much quicker than type 1 fibres. These fibres are suited to short duration, higher intensity activities such as 100m sprinting, throwing and jumping events.
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