The Structure and Functions of the Musculoskeletal System

• Sternocleidomastoid:

  • Helps with the breathing process.
  • All sporting events but particularly endurance events.
• Deltoid:

  • Abduction of the shoulder.
  • Outward arm action in a jumping jack.
• Rotator Cuffs:

  • A group of stabilising muscles at the shoulder, prevents dislocation, allows shoulder to rotate the humerus around its own axis.
  • Throwing action such as a javelin throw.
• Pectorals:

  • Adduction of the shoulder; Shoulder horizontal flextion.
  • Upwards phase of a press up.
• Intercostals:

  • Help with the breathing process.
  • All sporting activities but especially endurance events.
• Triceps:

  • Extend the elbow.
  • Shooting in netball.
• Biceps:

  • Flex the elbow.
  • Drawing a bow in archery.
• Abdominals:

  • Flex the trunk across the stomach.
  • Performing a sit up.
• Latissimus Dorsi:

  • Shoulder adduction; Shoulder horisontal extension.
  • Butterfly stroke in swimming.
• Quadriceps:

  • Extend the knee.
  • Kicking a ball in football.
• Hamstrings:

  • Flex the knee.
  • Performing a hamstring curl on a weights machine.
• Gastrocnemius:

  • Plantar flexion of the ankle
  • Standing on tiptoe to mark a goal shoot in netball.
• Tibialis Anterior:

  • Dorsiflextion of the ankle.
  • Foot making contact with a football.
• Types of Muscle Contraction:

  • Isotonic Contractions - occur when a muscle contracts and changes length.
  • Isotonic concentric contaction - Involves the muscle shortening.
  • Isotonic eccentric contraction - Involves the muscle lengthening whilst it is under tension.
  • Isometric Contraction - Involves a muscle producing tension but staying the same length. Occurs when body is fixed in one position.
• Antagonistic Muscle Pairs:

  • Biceps -> Triceps
  • Hamstrings -> Quadriceps
  • Gluteals -> Hip Flexors
  • Gastrocnemius -> Tibialis Anterior
  • Pectorals -> Latissimus Dorsi
• How antagonistic muscle pairs work at the elbow during the downwards and upwards phase of a press up:

  In the upward phase, the tricep contracts to extend the elbow, acting as the agonist, while the tricep relaxes and lengthens as the antagonist.

  In the downwards phase, the bicep contracts eccentrically to control the downward movement, acting as the agonist, while the tricep relaxes and lengthens to allow elbow flexion.
• Types of bone:

  • Long Bones:
  • E.g. Femur - Cylindrical in shape and found in the limbs. Main action is to act as a lever.
  • Short Bones:
  • E.g. Carpals - Small and compact, often equal in length and width. Designed for strength and weight bearing.
• Main Bones of the Skeleton:

  • Scapula (shoulder)
  • Humerus (upper arm)
  • Radius (ouside forearm)
  • Ulna (inside forearm)
  • Pelvis (hip)
  • Carpals (hand)
  • Femur (thigh)
  • Patella (knee)
  • Tibia (inside lower leg)
  • Fibula (outside lower leg)
  • Talus (ankle)
• Functions of the Skeletal System:

  • Movement.
  • Support.
  • Protection of vital organs by flat bones.
  • Production of blood cells.
  • Mineral storage.
  • Structural Shape.
• Synovial Joints:

  Freely moveable joints allow us the free movement to perform skills and techniques during physical activity.

  1. Hinge joint - found at the elbow, knee, and ankle. Allow flexion and extension of a joint.
  2. Ball and Socket - found at the shoulder and hip. Allow movemebt in almost every direction.
• Features of a Synovial Joint:

  • Synovial Fluid - lubricates the joint so it moves smoothly.
  • Synovial Membrane - makes the synovial fluid.
  • Cartilage - Cushions the joint and prevents friction and wear between bone ends.
  • Bursae - Fluid sacs which help prevent friction.
  • Joint Capsule - Prevents wear and tear on the bones.
  • Ligaments - connect bone to bone.
• Types of Joint Movement:

  • Flexion - Bending a joint. E.g. Bicep curl.
  • Extension - Straightening a joint. E.g. Elbow when putting a shot.
  • Abduction - Movement away from the midline of the body. E.g. Jumping Jack.
  • Adduction - Movement towards the midline of the body. E.g. Returning arms to their original position.
  • Rotation - The limb moves in a circular motion. E.g. Drive shot in golf.
  • Plantar Flexion - Pointing the toes. (only occurs at ankle) E.g. Pointing toes in ballet.
  • Dorsiflexion - Foot moves towards the shin (only occurs at the ankle), E.g. Pulling toes up.
• The musculoskeletal System:

  • Ligaments - Attach bone to bone.
  • Tendons - Attach muscle to bone

  Muscles contract to pull on bones to produce movement. Joints are able to move in a variety of directions to perform a range of sporting movements.