Exercise When Young May Reduce Risk Of Fractures Later In Life

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Exercise When Young May Reduce Risk Of Fractures Later In Life

http://www.medicalnewstoday.com/medicalnews.php?newsid=57947

Running and jumping during childhood is more than child's play; it

provides lifelong benefits for future bone health and appears to

reduce the risk of fractures later in life according to a Journal of

Bone and Mineral Research study by Indiana University-Purdue

University Indianapolis (IUPUI) researchers. The study is now

available in an advance online edition of the journal and will

appear in a print edition in 2007.

" Our study demonstrates that exercise when young may reduce the risk

of fractures later in life, and the old exercise adage of 'use it or

lose it' may not be entirely applicable to the skeleton, " said the

study's principal investigator, Stuart J. Warden, assistant

professor and director of research in physical therapy at the

Indiana University School of Health and Rehabilitation Sciences at

IUPUI.

Researchers exercised the right forearms of 5-week-old female rats

for a few minutes three times a week for seven weeks. The left

forearms were not exercised. Bone quantity and structure of the

rats' right and left forearms were assessed before and after

exercise. Researchers did not exercise the rats for the next 92

weeks -- virtually their entire lifespan. At that point, their

forearm bones were assessed again for bone quantity and structure,

as well as strength.

All procedures were performed following approval of the

Institutional Animal Care and Use Committee of Indiana University.

" We knew that exercise increases bone size and strength, and that

the skeleton is most responsive to exercise during the crucial

growing years around puberty when you reach adult size and

strength, " Warden said. " We also knew that bones are not as

responsive to exercise when you are older. "

What was not known, however, was if the skeletal benefits of

exercising while young would last a lifetime, Warden said. In other

words, he said, " can you use activity while young to offset the risk

of osteoporosis, or the risk of bone fractures, later in life " "

The study determined the answer to that question is, " Yes, " Warden

said.

The researchers found that the rats retained all of the skeletal

exercise benefits they obtained while young even though they hadn't

exercised for the rest of their lives, Warden said.

" We found the exercise resulted in a lifetime increase in bone size

in the right forearms of the rats and the bones of the left forearms

never caught up in size, " he said.

How big a bone is determines how resistant it is to bending, or how

strong it is, he said.

As humans age, bone loss occurs from the inside surface of the bone

outward, Warden noted. Exercising while young lays down additional

outside layers of bone. This results in a bigger bone than otherwise

would be the case.

" With more bone layers on the outside, you have more bone to lose, "

Warden said.

By making the right forearm bones bigger during growth in their

study, the researchers found these bones to be stronger, or more

resistant to fracture, than left forearm bones despite exercise

being ceased a lifetime ago.

The study demonstrates the importance of childhood exercise that

stimulates the skeleton, like basketball or jumping, Warden said.

Short periods of exercise several times a week are all that is

needed to stimulate bone development in children, he added.

The message to older adults, however, remains the same. Even though

the best time to gain lifetime bone health benefits is while people

are young, exercising when people are older is essential to maintain

bone mass and balance, as well as maintain aerobic fitness, all of

which aid in reducing the risk of low-trauma (osteoporotic)

fractures associated with aging.

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Co-authors of the study were Warden; Robyn K. Fuchs, Department of

Anatomy and Cell Biology, Indiana University School of Medicine,

IUPUI; Alesha B. Castillo, Department of Biomedical Engineering,

Purdue School of Engineering, IUPUI; Ian , Department of

Physical Therapy, School of Health and Rehabilitation Sciences,

IUPUI; and H. , Department of Orthopedic Surgery, IU

School of Medicine, IUPUI.

The National Institute of Arthritis and Musculoskeletal and Skin

Diseases, part of the National Institutes of Health, provided major

funding for this study.