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"The Effects of Decreased Hormonal Activity on Bone Loss and Muscular Development in Pre-, Peri-, Post- Menopausal Women"

By Velma Esprit Garnes

It is a known fact that advancing in aging has side effects and whether or not it is viewed negatively or positively is up to the beholder. Typically as women move into this stage of their life there is increased awareness of bone density loss.

Due to the significant decrease in the hormone estrogen, there is an increased incidence of vertebral and hip fractures. Estrogen is a critical hormone for the maintenance of bone mass in women.(1) Research shows that the most common remedy for the loss of the hormone estrogen is hormone replacement therapy (HRT) This is simply an attempt to replace the loss of the hormone estrogen (2).

Osteoporosis is a bone disease which affects 20 million women, particularly Caucasian, in the United States over the age of 40. The National Osteoporosis Foundation found that 1.3 million hip fractures are attributed to osteoporosis annually.

After menopause there is an increased amount bone loss due to the fact that estrogen production is significantly decreased. It is recommended that women undergo estrogen replacement therapy (ERT) in order to combat the degenerative effects of osteoporosis.

ERT is considered the most combative form of therapy and the most important intervention for the prevention of osteoporosis. There are a large number of fractures to the hip and spine due to the fact that osteoporosis is closely associated with the aging process. The loss of gait and balance contributes to increase falling incidents during the menopausal years.

Weight bearing activities such as high peak forces applied at high frequency rates result in the highest benefit in bone maintenance and enhancement. Weight training activities help to increase neuromuscular control and lead to improved balance and coordination.

This article summarizes several key factors, which lead to the prevention of bone loss: Effects of estrogen on bone and estrogen replacement therapy; the effects of weight bearing exercise on bone loss; and aerobic exercise consideration. While in adolescence and young adulthood exercise is of primary importance in preventing osteoporosis.

From the age of 35 it is estimated that women lose bone mass at the rate of 0.75% to 1% per year and this rate increases to 2 – 3% per year at menopause. In the initial 5 – 6 years after menopause the rate of bone loss is markedly more increased especially in the hip and spine. Women who participated in moderate to high intensity exercise for a significant portion of their life (athletes) in their premenopausal years were found to be more susceptible to increased bone mineral density (BMD) than nonathletic women.

Maintaining a high peak bone mass in adolescence and young adulthood is of primary importance in staving off osteoporosis and fractures later in life. Even though it is well known that exercise is important and contributes to decreased bone density, it is still unclear as to what frequency, intensity, type or duration of the activity would be most effective in preventing bone loss.

Dietary calcium supplementation seems to exert the greatest effect in the early years of peak bone formation before age 25 into 5 or more years beyond the onset of menopause. Calcium supplementation seems to best benefit individuals who have low calcium intake levels. There appears to be a synergistic effect with the combination of exercise with calcium supplementation as well as a synergistic effect of HRT with exercise.

Physical fitness and body composition can be improved in pre- and postmenopausal females and show no difference in their ability to alter body composition and improve cardio respiratory endurance.

In short there are positive effects of weight bearing activities, benefits to estrogen replacement in combination with exercise to combat osteoporosis, and calcium supplementation combined with exercise to increase lean body mass.

The impact of a 1-yr resistance-training program on body composition and muscle strength in postmenopausal women and the impact of HRT on body composition changes with and without exercise alongside dose-response relationships between measures of program compliance and changes in primary outcomes is evidenced by the fact that resistance and weight-bearing exercise significantly changes the body composition in postmenopausal women and their lean body mass (LBM).

Independently hormone therapy did not have an effect other than preserving the loss of LBM in postmenopausal women. LBM in women who exercised regardless of HRT status was increased. Significant fat weight loss was observed only in women who exercise while on HRT. Conclusively, resistance and weight-bearing exercise significantly changed the body composition in postmenopausal women and their LBM.

Hormone therapy showed no independent effects on body composition. Independently hormone therapy did not have an effect other than preserving the loss of LBM in postmenopausal women. Muscle forces cause the largest loads on bones and the largest bone strains, which in turn forces the bones to become stronger. With the increase of muscle also comes an increase in bone strength thereby increasing muscle and bone “mass”.

Aging adults lose momentary muscle strength, so their bone strain fall toward the remodeling threshold, this drop causes the bone to stop production and begins by removing bone next to the marrow contributing to the well-known loss of bone.

Vigorous exercise turns back the clock on the bone remodeling and reduces or stops further bone loss, which causes a greater need for intensity than most adults would try achieving.

To severely retard, or slow down the bone loss it is proven that HRT in combination with vigorous regimen of cardiorespiratory training, weight training, and weight bearing activities be included within a healthy program.

References:
1. Bemben, D.A, and N.L. Fetters. The independent and additive effects of exercise and estrogen and bone metabolism. J. Strength Cond. Res. 2000;14(1):114-120.

2. Burkhart. Exercise At Menopause: A Critical Difference. Medscape General Medicine 1999; 1(3).

3. Teixeira, Going, Houtkooper, Metcalfe, Blew, Flint-Wagner, Cussler, Sardinha, Lohman. Resistance Training in Postmenopausal Women with and without hormone therapy. Medicine & Science in Sports & Exercise. 2003; 35(4):555-562.

About the Author:

Velma Esprit Garnes resides in Gahanna, Ohio where she is a fitness freelance writer, professor and recently inducted into Columbus State Community College’s Sports Exercise Studies Hall of Fame. She can be through her website at www.studiotemple.com