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Effects of A Low Impact Exercise on Bone Density

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September 8, 2009
	Dr. Gary Huber : Head Medical Ego

(The following is an excerpt from an Ask Dr. Huber segment that we felt applied to many of our readers that participate in low-impact exercise. The specific question addressed bone density for women cyclists.)

Low impact sports, such as cycling, have been shown in studies to be at risk for loss of bone density for several reasons. First of all we (I too love cycling) strive to keep our cadence high which reduces the muscle fatigue and enhances our aerobic ability. But this very action reduces the overall force we generate on each stoke placing less demand on the bone. Cycling is a smooth, non-pounding sport so there is very little stimulus to the bone for growth. Both of these factors lead to very little osteogenic or bone growth signal. To add to this insult we tend to bike hard and long miles, which can lead to a rise in cortisol, our stress hormone, which in excess can be catabolic or destructive to bone. Now add the acidic nature of endurance sports and you have the body pulling calcium out of the bone to neutralize the lactic acid that comes with long endurance miles.

Higher Impact Choices
Compare this to power lifter or a runner. Both are placing a lot of strain on the skeletal system, the bones. When you put strain on a bone it responds with growth and will become thicker or more dense. So cyclists and others participating in low impact sports need to do some cross training or at the very least some weight training in the off season to fight this trend.

Perimenopausal and Menopausal Women
Now add the issue of being a perimenopausal women. Throughout your 40’s the amount of estrogen and progesterone you produce is on the decline so as you approach 50 years of age you are a beautifully matured work of art but without your HORMONES. It is the function of estrogen and progesterone to maintain your bone density by controlling the effects of osteoblasts and osteoclasts on bone regeneration. The classic picture we see is a demineralization of bone with a loss of density that accelerates at age 50 and beyond. This as well as other delights such as hot flashes and night sweats will lead many women to pursue answers in the form of hormone replacement. I will offer one loud warning: AVOID SYNTHETIC HORMONES.

Hormone Balance for Men & Women
A good part of my practice involves hormone balancing in men and women and I will only use BIO-IDENTICAL hormones. I strongly urge you to become very informed regarding hormone replacement and decide if this is an issue that appeals to you. Don’t allow anyone to talk you into hormone replacement until you have done some homework. Check out Women In Balance .org or read Dr. Northup’s book “The Secret Pleasures Of Menopause” or any number of other good texts on the subject. Hormone replacement can be a safe and very beneficial way to protect your brain your heart and your bones.

Vitamin D & Calcium
Beyond hormones and cross training I will recommend that you get your vitamin D level checked and begin supplementation with vitamin D if indicated. Without vitamin D you will not be able to absorb calcium effectively. I will also remind you that milk does not offer the calcium you think it does. Milk and dairy products will actually pull calcium from your bone, as it is an acidic animal food with very little bioavailable calcium. Rely on green vegetables for your calcium needs and keep your body alkaline. Avoid a low pH or acidic status as this will leach calcium from your bone and body and severely limit your aerobic and cycling ability. Get some simple pH paper from any drug store and check your saliva and urine pH. Keep salivary pH around 7.0 to 7.2 for good health in many areas. For more information on pH see my article I Have a Frog in My Throat & Other Adventures with My Blender