1Kicking a ball
In the backswing, the hamstrings contract to bend the knee. In the kick, the quadriceps contract to straighten it fast. This is biomechanics: muscles and bones working together.
hamstringsquadricepsbiomechanics
Lesson 13.4 notes
Movement and healthy bones
Muscles and bones working together, the energy muscles need, bones through life, and injuries and how they mend.
2Muscles need energy
Muscles need energy to contract. Respiration in muscle cells releases it, using glucose and oxygen brought by the blood. In hard exercise, muscles can tire: this is fatigue.
respirationfatigue
3Bones through life
Bone mass builds up until about age 30, then slowly falls. Women lose bone faster after the menopause, around 50. Very low bone mass, osteoporosis, makes bones break easily.
bone massosteoporosis
4Building strong bones
Weight-bearing exercise, such as running and dancing, makes bones denser. Bones also need calcium (milk, cheese, green vegetables) and vitamin D (sunlight, oily fish), which helps the body take in calcium.
calciumvitamin D
5Injuries
A fracture is a broken bone. A sprain is a stretched or torn ligament. A dislocation is a bone pushed out of its joint.
fracturespraindislocation
6Mending a fracture
A cast holds a broken bone still. A blood clot fills the gap, soft new bone grows, then it hardens. This takes about 6 to 8 weeks.
fracture
7Worn joints
In osteoarthritis (a type of arthritis), cartilage wears away, so bone rubs on bone and the joint is stiff and painful. A worn hip or knee can be replaced with metal and plastic parts.
osteoarthritiscartilage
Explore: Bones through life
Move through the ages and compare women and men. See what exercise and calcium when young do.
Common mistake: Ligaments and tendons are different
Ligaments join bone to bone and hold joints together. Tendons join muscle to bone and pass on the muscle's pull. A sprain damages a ligament.
Remember
- Biomechanics: muscles pull on bones, which turn at joints. The hamstrings bend the knee; the quadriceps straighten it.
- Muscles get energy from respiration. Bone mass builds up until about 30, then slowly falls; exercise, calcium and vitamin D keep bones strong.
- Fracture: a broken bone. Sprain: a stretched or torn ligament. Dislocation: a bone out of its joint. Arthritis: worn cartilage.
Going further at GCSE