Functional Anatomy Section Four: The Muscles

4.2 Identifying Muscles Trapezius Deltoid Biceps Triceps Pectoralis Major Latissimus Dorsi Rectus Abdominus Gluteus Maximus Hamstrings Quadriceps Gastrocnemius

4.3 Guide to Individual Muscles [A] PRIME MOVERS OF THE TRUNK 1.Rectus adbominus: Location : A group of two muscles running lengthwise along the medial aspect of the abdomen. They are rather like two columns of muscle running up either side of the belly button. They run from the pubis (pelvis) to the cartilage of the 5 th, 6 th and 7 th ribs. Movements:Rectus abdominus allows two basic movements. 1. Flexion of the trunk 2. Lateral flexion of the trunk Application: Typical sporting actions include: 1. Sit ups 2. Cartwheels 3. Pike in diving Rectus Abdominus

[A] PRIME MOVERS OF THE TRUNK 2. Erector Spinae Group: Location : One of the main muscles located in the lower back and one of the few visible. It runs from the pelvis to the lumbar vertebrae. Movements:Erector spinae group allows two basic movements. They are: 1. Extension of the spine 2. Lateral flexion of the trunk Application Typical sporting actions include: 1. Straightening out from a pike 2. Rowing 3. Swimming (body position) Erector Spinae

[B] PRIME MOVERS OF THE SHOULDER 1. Trapezius: Location : A large triangular muscle located on the posterior aspect of the body. It runs in a triangular shape from the base of the skull, the 7 th cervical vertebrae and all the thoracic vertebrae, to the scapula and clavicle. Movements:Trapezius allows four basic movements. They are: 1.Raise the head 2. Pull the shoulders back 3. Raise the scapula 4. Drop the scapula Application: Typical sporting actions include: 1. Pulling shoulder when throwing 2. Rowing 3. Looking up in basketball Trapezius

[B] PRIME MOVERS OF THE SHOULDER 2. Latissimus Dorsi: Location : The broadest muscle of the back. It forms the back of the armpit. This is a large triangular muscle which covers the lumbar and lower thoracic region of the back. It runs from the lower thoracic and lumber regions, to the anterior aspect of the humerus Movements:Latissimus dorsi allows three basic movements. They are: 1. Adduction of the upper arm 2. Extension of the shoulder 3. Internal rotation of the shoulder How can latissimus dorsi allow internal rotation of the shoulder to occur if it is a muscle located on the back? Because it attaches to the humerus Application: Typical sporting actions include: 1. Recovery in breaststroke 2. Ten-pin bowling 3. Drawing arm back to punch Latissimus dorsi

[B] PRIME MOVERS OF THE SHOULDER 3. Deltoid: Location : A triangular shaped muscle located on the superior aspect of the shoulder i.e. above the shoulder joint It runs from the scapular and clavicle to attach at the humerus Movements:Deltoid allows four basic movements. They are: 1. Flexion of the shoulder 2. Extension of the shoulder 3. Abduction of the arm 4. Rotation of the shoulder Application: Typical sporting actions include: 1. Throwing 2. Punching 3. Swimming Deltoid

[B] PRIME MOVERS OF THE SHOULDER 3. Pectoralis Major: Location : A large triangular muscle located on the chest. It runs from the clavicle, sternum and the 6 th rib, to the humerus. Movements:Pectoralis major allows three basic movements. These are: 1. Flexion of the shoulder 2. Abduction of the arm 3. Rotation (internal) of the shoulder Application: Typical sporting actions include: 1. Throwing 2. Punching 3. Press-ups Pectoralis major

[C] PRIME MOVERS OF THE ELBOW 1. Biceps Brachii: Location : A two-headed muscle (biceps) located on the anterior aspect of the humerus It runs from the scapular to the upper aspect of the radius Movements:Biceps allows two basic movements. They are: 1. Flexion of the elbow 2. Flexion of the shoulder Application: Typical sporting actions include: 1. Biceps curl 2. Rowing 3. Recovery in breaststroke Biceps Brachii

[C] PRIME MOVERS OF THE ELBOW 1. Triceps Brachii: Location : A large muscle located on the posterior aspect of the humerus. It runs from the scapular, over the posterior aspect of the humerus, to the upper part of the ulna. Movements:Triceps allows two basic movements. These are: 1. Extension of the elbow 2. Extension of the shoulder Application: Typical sporting actions include: 1. Karate chop 2. Press-up 3. Punching Triceps Brachii

[E] PRIME MOVERS OF THE HIP AND KNEE 2. Gluteus Maximus: Location : This is a the large fleshy muscle that makes up your backside. You are probably sitting on it right now! It is an extremely powerful muscle. It is located on the posterior aspect of the hip running from the ilium (pelvis), sacrum and coccyx to the upper third of the femur. Movements: Gluteus maximus allows three basic movements. 1. Extension of the leg 2. Abduction of the leg 3. External rotation of the leg (rotating outwards) Application: Typical sporting actions include: 1. Kicking 2. Running 3. Jumping

[E] PRIME MOVERS OF THE HIP AND KNEE 3. Quadriceps: Location : This is a group of four (quad) muscles located on the anterior aspect of the thigh. The four muscles making up the quadriceps group are: 1. Rectus femoris 2. Vastus medialis 3. Vastus lateralis 4. Vastus intermedius (not shown) Movements:Quadriceps allows two basic movements. 1. Extension of the knee 2. Flexion of the hip Application: Typical sporting actions include: 1.Kicking 2. Running 3. Jumping The Vastus intermedius is not shown because it lies under the Rectus femoris, so is not visible.

Consider the illustration. Label the muscles of the quadriceps group you can identify. Rectus femoris Vastus lateralis Vastus Medialis Vastus intermedius isn’t show as it lies under the other muscles!

[E] PRIME MOVERS OF THE HIP AND KNEE 3. Hamstrings: Location : This is a group of three muscles located on the posterior aspect of the thigh. Since they are in direct opposition to the quadriceps and are generally weaker they are prone to injury. The three muscles making up the hamstrings group are: 1. Semitendinosus 2. Biceps femoris 3. Semimembranosis Movements:Hamstrings allows two basic movements. These are: 1. Extension of the hip 2. Flexion of the knee Application: Typical sporting actions include: 1. Kicking 2. Running 3. Jumping

[F] PRIME MOVERS OF THE ANLKE 1. Gastroncnemius: Location : This is a the large fleshy muscle located on the posterior aspect of the lower leg. It runs from the distal aspect of the femur to the tarsal's (heel) via the Achilles tendon. Movements:Gastrocnemius allows two basic movements. These are: 1. Knee flexion 2. Plantar flexion Application: Typical sporting actions include: 1. Kicking 2. Pointing toes 3. Jumping

[F] PRIME MOVERS OF THE ANLKE 2. Soleus: Location : This muscle lies beneath gastrocnemius and serves largely the same function. It shares the Achilles tendon with gastrocnemius. It runs from the proximal aspect of both tibia and fibula to the same position as gastrocnemius on the heel Movements:Soleus allows one basic movements. 1. Plantar flexion Application: Typical sporting actions include: 1. Kicking 2. Pointing toes 3. Jumping

[F] PRIME MOVERS OF THE ANKLE 3. Tibialis anterior: Location : This muscle is located on the anterior aspect of the lower leg. It lies mainly over the tibia and can be felt running along its sharp edge. It runs from the proximal aspect of the tibia to the toes. Movements:Tibialis anterior allows two basic movements. 1. Dorsi flexion 2. Inversion Application: Typical sporting actions include: 1.Passing with the outside of the foot (soccer) 2.Kicking (recovery) 3. Rowing

4.4 Agonists and Antagonists When muscles create movement, they tend to work in pairs. When one muscle (or group), contracts to generate the movement, the opposing muscle (or group) relaxes. This is known as Reciprocal Inhibition. Each muscle in the pair is labelled as either the agonist or antagonist. Agonist: The muscle that produces the movement. Agonists are also referred to as prime movers. Why? Because they are the main muscle producing movement (prime = main). Antagonist: This muscle that opposes motion

Consider the example of a bicep curl. The movement occurring at the elbow is flexion The agonist muscle would be biceps The antagonist muscle would be triceps The prime mover would be biceps When the person extends the arm i.e. to lower the weight: The agonist muscle would be triceps The antagonist muscle would be biceps What other role does the antagonist muscle play in the lowering of the weight? Controls the speed at which weight is lowered in order to help prevent injury.