Muscles, bones and joints in movement
Physical Education · Key Stage 3 · The School
The frame
The skeleton supports the body, protects organs, and gives muscles something to pull against. The bones most often named in sport are the femur in the thigh, tibia and fibula in the lower leg, humerus in the upper arm, radius and ulna in the forearm, and the vertebrae of the spine. Bones do not move themselves — muscles move them.
Muscles pull in pairs
A muscle can only PULL, never push, so muscles work in ANTAGONISTIC PAIRS. At the elbow, the biceps contracts to bend the arm while the triceps relaxes; to straighten it, the triceps contracts and the biceps relaxes. The same arrangement appears at every joint — quadriceps and hamstrings at the knee, and so on.
Joints
Joints are named by the movement they allow. A HINGE joint bends one way — the elbow and knee. A BALL AND SOCKET rotates in many directions — the shoulder and hip. A PIVOT allows rotation, as at the top of the neck. The joint type sets the limits of what a movement can be, which is why technique differs so much between shoulder and knee actions.
Your elbow bends one way only, like a door: a HINGE joint. Your shoulder rotates in every direction: a BALL AND SOCKET. Your neck turns side to side on the top vertebra: a PIVOT. Your wrist moves in two planes but does not rotate freely: a CONDYLOID. Try moving each and describe the movement before naming the type — the shape of the joint is what allows the movement, not the other way round.