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:
- Increased 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
- Lack of exercise—especially weight bearing and resistance exercise
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 (some activities can be more than 1 type):
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:
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:
- Stair climbing
Resistance exercises use muscle strength to improve muscle mass and strengthen bone. Examples include:
Weight lifting, using:
- Free weights
- Weight machines
- Elastic tubing
- Calisthenics such as push-ups and chin-ups
- Warm up for five minutes before activity. This can consist of dynamic stretches that involve movement and a light walk.
- Start the activity slowly for the first five minutes.
Slowly increase your intensity so that your heart rate increases. A person doing moderate-intensity aerobic activity can talk. A person doing vigorous-intensity activity cannot say more than a few words without stopping to take a breath.
- Gradually increase your workout until you are working out at least 150 minutes a week at moderate–intensity or 75 minutes a week at vigorous intensity.
- Begin each exercise with light 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 ability to exercise.
2008 Physical Activity Guidelines for Americans. US Department of Health and Human Services website. Available at: http://www.health.gov/paguidelines/guidelines/default.aspx#toc. Published October 2008. Accessed February 12, 2014.
Bone remodeling. University of Washington website. Available at: http://courses.washington.edu/bonephys/physremod.html. Updated March 30, 2007. Accessed February 12, 2014.
How much physical activity do adults need? Centers for Disease Control and Prevention website. Available at: http://www.cdc.gov/physicalactivity/everyone/guidelines/adults.html. Updated December 1, 2011. Accessed February 12, 2014.
Osteoporosis. EBSCO DynaMed website. Available at: http://www.ebscohost.com/dynamed. Updated November 27, 2013. Accessed February 12, 2014.
Skeleton keys. Smithsonian Museum of Natural History website. Available at: http://anthropology.si.edu/writteninbone/young_old.html. Accessed February 12, 2014.
Last reviewed February 2014 by Michael Woods, MD
Please be aware that this information is provided to supplement the care provided by your physician. It is neither intended nor implied to be a substitute for professional medical advice. CALL YOUR HEALTHCARE PROVIDER IMMEDIATELY IF YOU THINK YOU MAY HAVE A MEDICAL EMERGENCY. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with any questions you may have regarding a medical condition.
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