The Muscular System There are three types of muscles in the human body: Cardiac muscle: a type of involuntary muscle that works automatically. It is only found in the heart and is special because it never rests. Involuntary muscle: also known as smooth muscle, they are not controlled but they work automatically. They are found in the intestines, blood vessels and urinary organs. Voluntary muscle: the most common muscle type. These attach to the skeleton and we can control these and move them, using signals from the brain. They help us run, jump, throw and perform all sporting skills. (GCSE PE: Unit 1.2.2)

The Muscles Upper Body muscles: Trapezius Deltoid Latissimus dorsi There are 11 specific muscles that you need to know. You will need to know where they are found in the body and what movement they produce. Upper Body muscles: Trapezius Deltoid Latissimus dorsi Pectorals Biceps Triceps Abdominals Lower Body muscles: Gluteus maximus Quadriceps Hamstrings Gastrocnemius (GCSE PE: Unit 1.2.2)

Antagonistic Pairs Agonist/Antagonist Muscles are arranged in antagonistic pairs, so when one muscle contracts and pulls, the other relaxes to allow the joint to work For example; The biceps and triceps are arranged in an antagonistic pair to allow movement in the forearm. Agonist/Antagonist In these pairs, there is always an agonist and an antagonist. The agonist muscle is the contracting muscle and the antagonist is the relaxing muscle. For example, when we extend our lower arm, the triceps contract (so it is the agonist) and the bicep relaxes (so it is the antagonist). When we flex our lower arm, this muscles switch roles. The biceps contracts (so becomes the agonist) and the triceps relax (so they become the antagonist). (GCSE PE: Unit 1.2.2)

Muscle Contractions There are two main types of muscle contraction that you need to know: Isotonic Contractions: These are contractions that cause a change in a muscles length. They are the main contraction we have spoken about so far. Examples include; a bicep curl, kicking a football, throwing a ball, doing a sit-up. Isometric Contractions: This are contractions where the muscle length stays the same. They are used to keep the body steady, for example; doing a plank, handstands, pushing in a rugby scrum. (GCSE PE: Unit 1.2.2)

Muscle Fibres When we want to move our body, our brain sends signals to the special fibres within the muscles and these allow the movement to happen. There are two different types of fibre in the muscles; fast twitch and slow twitch muscle fibres. Every person has a natural combination of both in their body and this amount cannot be changed. 1) Fast Twitch muscle fibres: These are used in sports that require short bursts of energy. They contract fast (hence the name) and produce a powerful movement. They only have a limited oxygen supply and so tire quickly. They are best used for speed events, for throwing or for jumping. 2) Slow Twitch muscle fibres: These are used in longer, endurance sports. They have a very good oxygen supply and this gives them large amounts of energy. They can contract any times and stay efficient over long periods. They are best used in long-distance running, cycling or swimming. (GCSE PE: Unit 1.2.2)

Muscle Movements There are a few different muscle movements that you need to be aware of: Flexion: This occurs when a body part is bent (the angle at the joint is decreased). Extension: This is when a body part is straightened (the angle at the joint increases). Adduction: This is where a body part is brought towards the centre (it is added to the body). Abduction: This is where a body part is moved away from the bodies centre. Rotation: The angle of the joint does not change but the joint moves in a circular motion. (GCSE PE: Unit 1.2.2)

Muscle Movements In addition, there are two extra movements that you need to know. These are both specific to the foot and toes. Plantar Flexion: Is the action of pointing your toes (standing on tip-toes) and moving them further away from the body. Dorsi Flexion: This is when you lift your toes closer towards your body. (GCSE PE: Unit 1.2.2)

Upper Body 1) Trapezius Attached to the back of the neck and the shoulder. Movement: Rotation at the shoulder (GCSE PE: Unit 1.2.2)

Upper Body 2) Deltoid Attached to the top of the shoulder and the upper arm. Movement: Abduction at the shoulder (GCSE PE: Unit 1.2.2)

3) Latissimus dorsi Upper Body A sheet of muscle which connects from the lower spine to under the upper arm. Movement: Adduction of the shoulder (behind the back) (GCSE PE: Unit 1.2.2)

4) Pectorals Upper Body Covers the chest. Movement: Adduction of the shoulder (in front of the body) (GCSE PE: Unit 1.2.2)

5) Biceps 6) Triceps Upper Body Attached at the top of the shoulder and the elbow. Triceps allows extension at the elbow. Biceps allows flexion at the elbow. When the arm is extended (straightened), the triceps contracts and the biceps relaxes. When the arm is flexed (bent), the triceps relaxes and the biceps contracts (GCSE PE: Unit 1.2.2)

7) Abdominals Upper Body They are found across the front of the stomach. Movement: Flexion in the torso. (GCSE PE: Unit 1.2.2)

1) Gluteus maximus Lower Body These form the buttocks and attach to the upper leg. Movement: Extension of the hip. (GCSE PE: Unit 1.2.2)

2) Quadriceps Lower Body Found on the front of the upper leg. They attach at the hip and the knee. Movement: Extension of the knee. (GCSE PE: Unit 1.2.2)

3) Hamstrings Lower Body Found on the back of the upper leg. They attach at the bottom of the buttocks and the back of the knee. Movement: Flexion of the knee (GCSE PE: Unit 1.2.2)

4) Gastrocnemius Lower Body Found on the back of the lower leg. It starts at the back of the knee and extends down to the ankle. Movement: Extends the ankle (and allows pointing of toes – plantar flexion) (GCSE PE: Unit 1.2.2)

Immediate Effects of Exercise on the Muscular System Exercise has a number of effects on our muscles. As soon as we start exercising, our muscles start to feel some of those effects: Muscle Fatigue: Muscles begin to get tired as our ability to use oxygen becomes less efficient. Lactic Acid build-up: Anaerobic exercise causes lactic acid to build up due to the lack of oxygen – this causes pain and cramp. Increase in muscle temperature. Increase in C02 production. (GCSE PE: Unit 1.2.2)

Long-term Effects of Exercise on the Muscular System Exercise has a number of effects on our muscles. If we train our muscles over time the following effects happen: Muscle Hypertrophy: Muscles increase in size and strength – which leads to increased power, muscular strength and muscular endurance. Increase in myoglobin stores: Myoglobin helps store oxygen in the muscles. Extra myoglobin improves oxygen supply and means more energy can be made with every contraction. Tendons and Ligaments get stronger: Tendons and ligaments hold the muscles in place. They get stronger and this makes them thicker and more flexible, giving better joint support. (GCSE PE: Unit 1.2.2)

Muscle Injuries When exercising, there is always a risk of muscular injury. Soft Tissue Injuries: There are two main types here; strains and sprains. - Strains: occur when a muscle is overstretched or torn (eg a pulled muscle). - Sprains: occur when ligaments are overstretched or torn around a joint (eg twisted or sprained ankle). Overuse Injuries: These are caused by using a part of the body again and again. They damage the tendons and an example is tennis elbow. (GCSE PE: Unit 1.2.2)

Muscle Injuries - Prevention There are a number of steps you can take to prevent injury: Warm-up: Allows the muscles to warm-up (extra blood flow) and avoid strains. Cool-down: Allows the muscles to cool down slowly and prevents lactic acid build up. Rest: This prevents overuse injuries. It also allows muscles time to repair themselves. HOWEVER, too much rest can lead to muscle atrophy (where muscles get smaller and weaker – just like Mr Drake). (GCSE PE: Unit 1.2.2)