So the theory goes something like this: Osteoporosis develops as your bone mineral density decreases, which happens with age (after menopause it can really accelerate). Your peak levels are in your mid 30’s. The higher you can get your bone mineral density at that point, the longer you will be able to stave off osteoporosis.

Two really important factors for increasing your bone mineral density (BMD) are diet/nutrition, and exercise (traditonally weight bearing exercise such as walking has been championed, but also resistance exercise, that is, weights, have been shown to be beneficial). Some studies have measured the peak level of bone mineral density in certain bones to be attained before the age of 20 (one study found for the female femur, or thigh bone, the peak was attained at 14.1 years of age!), but most reports conclude that your BMD will continue to rise through your 20’s and peak in your 30’s.

There have been plenty of reports suggesting you should really work hard in your 20’s to get plenty of calcium etc into your diet, and to exercise at this time, but this study shows that you can start even earlier and get benefits – as early as your teens.

This study measured both BMD and bone mineral content (BMC); the former measures, as the name would suggest, the density of the bones, the latter measures the total bone mass. The study was done on women aged between 52-73, who were divided according to the type of exercise they did in their teens – some 40+ years earlier.

Now, there is a lot of water under that bridge, right. I mean, a lot of factors contribute to the state of your bones. But the results were pretty clear – “Women who had participated in high-impact, weight-bearing activities (eg running) during their teen years had significantly greater BMC in both the lumbar spine and femoral neck than their less active counterparts (eg swimming)”.

It’s good to know that being active at this time will be useful. The more information you have, the more prepared you can be for what lays ahead. The results of this study indicate that being active early in your life will reap benefits later.

Weight-Bearing Exercise During Adolescence Benefits Bones Decades Later

NEW YORK (Reuters Health) Dec 30 08 – Women who participated in weight-bearing sports during their teens, the formative years for bone growth, have stronger bones after menopause than women who participated in lighter activities during their youth.
Those findings, from investigators in Japan, are published in the December 23rd Online First edition of the British Journal of Sports Medicine.

Dr. Takeru Kato at Suzuka University and colleagues assessed bone health among 46 postmenopausal women between 52 and 73 years of age. The women were grouped according to what types of activities they had participated in between the ages of 12 and 18 years. There were 16 women who participated in high-impact, weight-bearing activities, such as running and jumping, and 30 who participated in low-impact, non-weight-bearing exercises, such as swimming, or very little exercise.

The investigators measured bone mineral content (BMC) and bone mineral density (BMD) of the lumbar spine and femur on dual energy X-ray absorptiometry (DXA). They used magnetic resonance imaging (MRI) to measure bone size, shape and characteristics, including the mid-diaphyseal cross-sectional area of the femur, periosteal and endosteal perimeters, and maximum and minimum second moment of area.

Women who had participated in high-impact, weight-bearing activities during their teen years had significantly greater BMC in both the lumbar spine and femoral neck than their less active counterparts. They also had significantly greater femoral mid-diaphyseal bone cross-sectional area, periosteal perimeters, and maximum and minimum second moment of area than the non-weight-bearing groups.

BMD did not differ significantly between the two groups.

“Adolescent weight-bearing exercise exerts preservational effects on femoral mid-diaphyseal size and shape, while DXA-measured BMC effectively identified the same tendency,” Dr. Kato and colleagues conclude. Weight-bearing activity during the formative years shows positive effective on bone health, “even after 40 years.”

Br J Sports Med 2008.