Secondary Logo

Journal Logo

Building (and Keeping) Strong Bones

Bushman, Barbara A. Ph.D., FACSM

doi: 10.1249/FIT.0b013e3182a951b8
DEPARTMENTS: Wouldn’t You Like to Know?
Free

What steps can be taken to promote bone health — both in youth and throughout the life span?

Barbara A. Bushman, Ph.D., FACSM, is a professor at Missouri State University. She holds four ACSM certifications: Program Director, Clinical Exercise Specialist, Health Fitness Specialist, and Personal Trainer. Dr. Bushman has authored papers related to menopause, factors influencing exercise participation, and deep water run training; she authored ACSM’s Action Plan for Menopause (Human Kinetics, 2005), edited ACSM’s Complete Guide to Fitness & Health (Human Kinetics, 2011) and promotes health/fitness at http://www.Facebook.com/FitnessID.

Disclosure: The author declares no conflict of interest and does not have any financial disclosures.

Figure

Figure

Q:WHAT STEPS CAN BE TAKEN TO PROMOTE BONE HEALTH — BOTH IN YOUTH AND THROUGHOUT THE LIFE SPAN?

A:Bones are dynamic structures within the body, made up of collagen (which provides a flexible framework for bone), calcium-phosphate mineral complexes (which provides strength and hardness), and bone cells (which are involved in the breakdown and buildup of bone) (11). Ideal bone tissue characteristics include optimal levels of stiffness, flexibility, and lightness and must be able to adapt to changes in physiological and mechanical environments (5). For youth, the dynamic nature of bone is very apparent during growth when bones change in size and shape, a process called modeling (14). In adulthood, bone is more stable but still constantly is being remodeled, a process where older bone is removed and is replaced by new bone — a “preventative maintenance program” (12).

Many factors affect bone balance, resulting in either stable status or a net gain or loss of bone (Figure 1) (1). Bone loss occurs when more bone is removed than replaced; loss of bone increases fracture risk (12). Promoting bone health is important throughout the life span: “At any age, the amount and quality of a person’s skeleton reflect everything that has happened to it from uterine existence through the years of growth into young adult life when the maximum investment in bone is achieved and later when progressive loss of bone often predominates” (6). Focusing on bone early in life is key because up to 90% of peak bone mass is reached by 18 years of age in females and 20 years of age in males (10), with peak bone mass attained by the end of the third decade (7). Bone mass decreases about 0.5% per year after the age of 40 years, and bone loss is more rapid for women at menopause (7).

Figure 1

Figure 1

Figure 2

Figure 2

The “silent” nature of bone loss is significant because osteoporosis does not present with warning signs before fracture (12). Osteoporosis is diagnosed by a bone mineral density (BMD) more than 2.5 SD below the mean peak value for young normal adults, thus compromising bone strength (3). Osteoporosis development can be attributed to inadequate accumulation of peak bone mass and/or to excessive rate of bone loss (4). Being aware of situations that may place bones at risk is valuable — an interactive bone health checkup is available from the National Institutes of Health (see http://www.niams.nih.gov/Health_Info/Bone/Optool/index.asp) (9). The information is based on the U.S. Surgeon General’s Report on Osteoporosis and Bone Health. For more on the prevalence and cost of osteoporosis, see Box 1 and Figure 2. In addition, the National Osteoporosis Foundation (NOF) suggests various interventions to reduce fracture risk (see Box 2).

Bone health is impacted by many factors — some of which cannot be controlled (e.g., age, family history) as well as factors that can be modified, including diet and physical activity. For full benefits of exercise to be realized, adequate energy intake as well as sufficient calcium are needed (4). The Surgeon General’s Report points out that, unfortunately, many Americans do not exercise enough nor consume enough calcium and vitamin D to optimize bone health (14). The remainder of this article will focus on physical activity and exercise training, as well as nutritional factors that promote bone health.

The ACSM Position Stand on Physical Activity and Bone Health points out two strategies to make the skeleton more resistant to fracture (7):

Figure

Figure

  • Maximize the gain in BMD during the first three decades of life.
  • Minimize the decline in BMD after the age of 40 years caused by endocrine changes, age, decline in physical activity, and other potential factors.

When considering exercise training, the Position Stand includes the following principles for consideration (7):

BOX 1

BOX 1

BOX 2

BOX 2

  • Specificity: adaptation occurs in bone exposed to changes in daily loading forces
  • Overload: adaptations require the loading stimulus to exceed usual conditions, and a progressively increasing overload is needed for continued adaptation
  • Reversibility: if exercise is reduced, benefits to bone may not persist (further research is needed to determine the rate of bone loss and the impact of age on reversibility)

To promote gains in bone mass, children should include relatively high-impact andstrengthening activities (7). With increases in age during adulthood, the benefits of exercise are more likely in attenuating bone loss rather than expecting bone mass increases (7). For adults, regular physical activity may help with fracture prevention in a couple of ways: preserving bone mass and/or reducing falls (7). Physical activity is part of both primary and secondary prevention of osteoporosis (2).

Figure

Figure

The Surgeon General’s Report suggests that weight-bearing or impact-type activities are the most beneficial for increasing or maintaining bone mass, although non-weight-bearing or low-impact activities may help with prevention of falls by improving balance and coordination and maintaining muscle mass (14). For anyone with osteoporosis, and in particular for those who have experienced a fracture, consultation with a physician is recommended to determine specific limitations, as well as exercises that may be contraindicated (e.g., movements involving twisting or excessive trunk flexion) (3). For a summary of general recommendations for healthy bones found in the ACSM Position Stand, see Table 1. A sample multimodal exercise program is shown in Table 2.

TABLE 1

TABLE 1

TABLE 2

TABLE 2

In addition to the potential benefits of physical activity on bone health, diet is another modifiable factor. Adequate calcium intake is vital — both for achieving peak bone mass and for maintaining bone health (12). To maintain blood calcium levels, proper dietary intake is needed to prevent calcium being taken from the skeleton where 99% of the body’s calcium is stored (12). The recommendations from the NOF for dietary intake of calcium for older adults are in line with those of the Institutes of Medicine: 1,000 mg/d for men aged 50 to 70 years and 1,200 mg/d for women age 51 and older and men 71 years and older (12). For calcium recommendations throughout the life span, see Table 3.

TABLE 3

TABLE 3

Sources of calcium include dairy products (with low-fat or nonfat dairy products being recommended because they have the full amount of calcium but avoid excess fat), fortified food (e.g., calcium-fortified orange juice), and some fruits and vegetables (14). Obtaining nutrients from food typically is recommended; however, fortified food and supplements may be helpful for individuals whose dietary intake falls short (14). The tolerable upper intake levels for calcium vary with age (8):

  • 1,000 mg for 0 to 6 months of age
  • 1,500 mg for 7 to 12 months of age
  • 2,500 mg for 1 to 8 years old
  • 3,000 mg for 9 to 18 years old
  • 2,500 mg for 19 to 50 years old
  • 2,000 mg for those 51 years and older

Getting too much calcium is rare when relying on food alone; excess intakes are more likely for those taking supplements (8). Kidney stone formation is associated with a high intake of calcium from supplements, and some studies link a high calcium intake with an increased risk of cardiovascular disease (8).

Vitamin D is needed for calcium absorption and bone health (12). Recommendations for vitamin D intake from NOF include 800 to 1,000 IU of vitamin D per day for adults age 50 years and older (12). The 2012 Surgeon General’s Report on “Bone Health and Osteoporosis: What It Means to You” points out the increasing vitamin D needed with advancing age: 400 IU from age 0 to 12 months, 600 IU from age 1 to 70, and 800 IU for those older than 70 years (15). Vitamin D can come from sunlight (exposure to sunlight results in conversion of precursors in the skin to active vitamin D), as well as dietary sources of vitamin D like fortified milk and fish (e.g., herring, salmon, tuna, sardines). Often, vitamin D is included with calcium supplements, but avoid consuming more than 2,000 IU per day (tolerable upper level) (14).

In summary, physical activity and diet are lifestyle factors that have the potential to promote bone health throughout the life span. As stated in the Surgeon General’s Report (14): “Physical activity and adequate calcium and vitamin D intake are now known to be major contributors to bone health for individuals of all ages. Even though bone disease often strikes late in life, the importance of beginning prevention at a very young age and continuing it throughout life is now well understood.”

Back to Top | Article Outline

References

1. American College of Sports Medicine. ACSM’s Complete Guide to Fitness & Health. Bushman BA, editor. Champaign: Human Kinetics; 2011, 396 p.
2. American College of Sports Medicine. ACSM’s Guidelines for Exercise Testing and Prescription. 9th ed. Philadelphia (PA): Lippincott Williams & Wilkins; 2014, 456 p.
3. American College of Sports Medicine. ACSM’s Resource Manual for Guidelines for Exercise Testing and Prescripton. 7th ed. Philadelphia (PA): Lippincott Williams & Wilkins; 2014, 862 p.
4. Borer KT. Physical activity in the prevention and amelioration of osteoporosis in women: Interaction of mechanical, hormonal and dietary factors. Sports Med. 2005; 35 (9): 779–830.
5. Guadalupe-Grau A, Fuentes T, Guerra B, Calbet JAL. Exercise and bone mass in adults. Sports Med. 2009; 39 (6): 439–68.
6. Heaney RP, Abrams S, Dawson-Hughes B, Looker A, Marcus R, Matkovic V, Weaver C. Peak bone mass. Osteoporosis Int. 2000; 11: 985–1009.
7. Kohrt WM, Bloomfield SA, Little KD, Nelson ME, Yingling VR. Position stand: Physical activity and bone health. Med Sci Sports Exerc. 2004; 36 (11): 1985–96.
8. National Institutes of Health Office of Dietary Supplements. Dietary Supplement Fact Sheet: Calcium. Bethesda (MD): Office of Dietary Supplements; [cited 2013 May 15]. Available from: http://ods.od.nih.gov/factsheets/Calcium-HealthProfessional/.
9. National Institutes of Health Osteoporosis and Related Bone Diseases National Resource Center. Check Up on Your Bones. Bethesda (MD): Osteoporosis and Related Diseases National Resource Center; [cited 2013 May 15]. Available from: http://www.niams.nih.gov/Health_Info/Bone/Optool/index.asp.
    10. National Institutes of Health Osteoporosis and Related Bone Diseases National Resource Center. Kids and Their Bones: A Guide for Parents. Bethesda (MD): Osteoporosis and Related Diseases National Resource Center; July 2012 [cited 2013 May 15]. Available from: http://www.niams.nih.gov/Health_Info/Bone/Bone_Health/Juvenile/default.asp.
    11. National Osteoporosis Foundation. [Internet]. Bone Basics. Washington (DC): National Osteoporosis Foundation; [cited 2013 June 8]. Available from: http://www.nof.org/learn/bonebasics.
    12. National Osteoporosis Foundation. Clinician’s Guide to Prevention and Treatment of Osteoporosis. Washington (DC): National Osteoporosis Foundation; 2013; [cited 2013 May 15] Available from: http://nof.org/hcp/resources/913.
    13. National Osteoporosis Foundation. [Internet]. NOF Releases New Data Detailing the Prevalence of Osteoporosis. Washington (DC): April 18, 2013 [cited 2013 May 15]. Available from: http://www.nof.org/news/1009.
      14. U.S. Department of Health and Human Services. Bone Health and Osteoporosis: A Report of the Surgeon General. Rockville (MD): U.S. Department of Health and Human Services, Office of the Surgeon General; 2004.
      15. U.S. Department of Health and Human Services. The Surgeon General’s Report on Bone Health and Osteoporosis: What It Means to You. Rockville (MD): U.S. Department of Health and Human Services, Office of the Surgeon General; 2012.
      © 2013 American College of Sports Medicine.