As noted in a previous post, bones matter! Our skeletal frame defines our basic shape, protects our vital organs, and serves as the scaffolding on which all of our soft tissues hang. It undergoes tremendous growth between infancy and adulthood, achieving peak bone mass somewhere between age 20 and 30. Bone remodeling remains a mainstay of our physiology for a lifetime, constantly absorbing old and weakened bone to make way for deposit of stronger material.

Healthy bodies balance bone excavation and bone building via osteoblasts and osteoclasts, respectively. When osteoclast activity outpaces osteoblasts, a diagnosis of osteopenia or osteoporosis may result. Commonly prescribed pharmaceuticals (e.g., Fosamax, Boniva, Reclast, Prolia) put the brakes on osteoclast activity, but the question remains: What can I do to build bone once I’ve lost it?

There are a couple of bone building pharmaceuticals (e.g., Forteo, Evenity), but they’re quite spendy and generally reserved for folks with severe bone loss. Fortunately, there is a low cost, accessible, easily customizable alternative: EXERCISE!

Physical activity generates external and internal forces on the skeleton. The resulting mechanical strain and vibration in the bones stimulates stem cells to differentiate into osteoblasts and osteoclasts, thereby increasing bone turnover and promoting bone growth. Bone density and bone quality improve while squeezing out fat in the bone marrow. Not surprisingly, a history of vigorous physical activity is associated with stronger outer (cortical) bone, greater cross-sectional support (trabecular), and higher bone mineral density (BMD).

For postmenopausal women seeking to build bones, a recent study determined the effects of low, moderate, and high intensity exercise on BMD at the spine and hip in postmenopausal women.¹ It covered 53 trials testing 63 interventions: 19 low, 40 moderate, 4 high intensity. Consider exercise intensity as follows:

• LOW: 40-50% of your maximum heart rate (MHR)² – e.g., a casual walk, a stretch session, a beginners’ yoga class or tai chi, bike riding, using an elliptical trainer at an easy pace
• MODERATE: 50-70% of your MHR – e.g., brisk walking, walking uphill, jogging, using an elliptical trainer at a faster pace
• HIGH: 70-85% of your maximum heart rate – e.g., running at a heart-pounding pace, High Intensity Interval Training (HIIT), jumping, aerobics, or any other impact-oriented vigorous activity where you can say but a few words before having to breathe

Results of the highest quality trials suggest that a combination of progressive resistance and impact training at moderate to high intensity appears to be the most effective regimen to improve bone strength at the spine and hip. Low intensity exercise does not appear to be efficacious, though some benefit has been registered in the femoral neck. For those who enjoy walking, the research suggests a spirited pace at 75% or greater MHR or walking with a weighted vest. Non-impact aerobics such as cycling or swimming have shown little to no effect on preventing age-related bone loss.

In another study on postmenopausal women,³ participants were randomly assigned to groups and tasked with hopping 50 times on each foot for either 0, 2, 4, or 7 days a week for 6 months. The 7-day a week group built significantly more bone during the study period. Not bad for such a simple intervention!

Of course, weight-bearing exercise may be contraindicated for folks with severe osteoporosis or osteoarthritis. Mechanical loading may also be ill-advised for those with diseased cartilage. And individuals with cardiovascular health problems may not be able to engage in the vigorous exercise recommended for BMD improvement. A consultation with a physician makes good sense.

Finally, bone guru Dr. R. Keith McCormick gives a big “thumbs up” to exercise in his masterpiece, Great Bones. He cites several benefits:

• Increased muscle tone and strength
• Improved coordination and balance
• Tightened core muscles
• Increased join flexibility
• Reduced fall risk (which really matters to folks with osteoporosis!)
• Enhanced circulation
• Reduced systemic inflammation (which dampens osteoclast activity)
• Improved mitochondrial function (which boosts energy)
• Elevated protein synthesis
• FUN!

He prefers short bouts of exercise (30 minute sessions) for resistance training (3+ days/week) and endurance training (3+ days/week) as excess stress combined with inadequate rest are bad for bones. His recipe for bone health calls for:

Notes:

¹ Melanie Kistler-Fischbacher, Benjamin K. Weeks, Belinda R. Beck, The effect of exercise intensity on bone in postmenopausal women (part 2): A meta-analysis, February 2021

² Multiply your age by 0.7 and subtract the total from 208 to get your maximum heart rate.

³ Christine A. Bailey, Katherine Brooke-Wavell, Optimum frequency of exercise for bone health: Randomised controlled trial of a high-impact unilateral intervention, April 2010