Bone Health and Osteoporosis Notes

Weight-Bearing Exercise Benefits:
- Stimulates osteoblasts, increasing bone deposition and decreasing resorption.
- Mechanical stress from skeletal muscle pull and gravity strengthens bones.
- Stronger muscles exert a stronger pull on bones, stimulating them to thicken.
- Builds both bone mass and skeletal muscle mass.
- Examples: Walking with added weight (
  rucksack, weighted vest), moderate weightlifting, bodyweight exercises (push-ups, pull-ups,
  squats, planks).
- Lack of weight-bearing exercise (bed rest, zero gravity) leads to bone and muscle loss.

Bone Deposition vs. Resorption:
- Birth to adolescence: Deposition ( $>$ ) Resorption.
- Young adulthood: Deposition ( $\approx$ ) Resorption.
- Middle age and beyond: Resorption ( $>$ ) Deposition, leading to decreased bone mass.
Hormonal Influence:
- Decrease in sex hormones (especially estrogen in women post-menopause, approx. ages $45$ -
  55) is a major factor.
- Estrogen is crucial for bone health.
Gender Differences: Females generally have smaller, less dense skeletons, increasing their risk of bone loss during aging.
Collagen Loss: Diminished collagen (most plentiful protein) makes bones more brittle and less flexible.