Bone is living tissue that is constantly undergoing a process called remodeling. In remodeling, cells called osteoclasts are breaking down old bone, as cells called osteoblasts are replacing it with new tissue. Many factors can affect the remodeling process and leave you with bones that are less dense and more fragile.

Some factors that affect bone remodeling are:

  • Advancing age
  • Low vitamin D—The body makes vitamin D in response to sunlight. You can also get vitamin D by eating certain kinds of food or by taking a supplement.
  • Diet low in calcium
  • Smoking
  • Lack of exercise (especially weight bearing and resistance exercise)

Why Exercise Is Good for Bones

Regular weight-bearing and resistance exercise helps build muscle, as well as maintain and increase bone strength. Exercise causes the muscle to contract against the bone. This action stresses or stimulates the bone, and the bone becomes stronger and denser. The three main types of exercise are:

Aerobic (Cardiovascular) Exercise

In aerobic exercise, you continually move large muscles in the legs, shoulders, and buttocks. This action causes you to breathe more deeply, and your heart to work harder pumping blood, thereby strengthening your heart and lungs. Examples include:

Weight-Bearing Exercise

In weight-bearing exercises, your bones and muscles work against gravity, and your feet and legs bear the weight. Your bones adapt to the weight and pull of the muscle during weight-bearing exercise. Examples of weight-bearing exercises include:

  • Jogging
  • Walking
  • Stair climbing
  • Dancing
  • Soccer

Resistance Exercise (Strength Training)

Resistance exercises use muscle strength to improve muscle mass and strengthen bone. Examples include:

  • Weight lifting, using:
    • Free weights
    • Weight machines
    • Elastic tubing
  • Calisthenics (eg, push-ups, chin-ups)

Tips for Beginning:

Aerobic or Weight-bearing Exercise

  • Warm up for five minutes before activity. This can consist of stretches and a light walk.
  • Start the activity slowly for the first five minutes.
  • Slowly increase your intensity so that your heart rate increases to 60% to 70% of your maximum heart rate. Maximum heart rate equals 220 minus your age. To find your heart rate:
    • Place your index and middle finger over your pulse on your wrist or the side of your neck.
    • Count your pulse for 15 seconds.
    • Multiply this number by four; this is your heart rate.
  • Gradually increase your workout until you are working out at 60% to 70% of your maximum heart rate for the entire 20-minute workout at least three days a week. Make sure to include 5-10 minute warm-up and cool down sessions.

Resistance Exercise

  • Begin each exercise with very low weights and minimal repetitions.
  • Slowly (over weeks) increase weight, never adding more than 10% in a given workout.
  • Do these exercises 2-3 times a week. Allow for one day between each workout for your bones and muscles to rest and repair themselves.
  • Gradually increase the number of repetitions to 2-3 sets of 8-10 repetitions with a rest period of 30-60 seconds between sets.
  • Although stiffness the day after exercise is normal, if you are in pain, you did too much. Decrease the intensity or the duration of your exercise.

Before starting any type of exercise program, check with your doctor about any possible medical problems you may have that would limit your exercise program.