Like muscle, bone is a living tissue that responds to exercise by becoming stronger. Osteoporosis is a disease that strikes the bones, making them weaker and more susceptible to breaks.
Osteoporosis is more prevalent in women.
Young men and women who exercise regularly achieve greater bone density and strength than those who don't. You have until about age 35 to attain the maximum bone strength, and then you begin to lose it. Those over age 35 can slow bone loss with regular exercise.