A woman's hormones provide the script for the exquisitely fine tuned biological program that enables her to bear children. Obviously, her body is expressly designed to get pregnant and give birth and breastfeed. But the same hormones that make these functions possible have surprising effects on other body systems, too.
Hormones play an important role where muscle is concerned, for example. Women have comparatively high levels of estrogen and low levels of testosterone, while men have comparatively low levels of estrogen and high levels of testosterone. Since testosterone stimulates muscle growth, men have more muscle mass than women do. Yet women need muscle strength, which is one of the reasons why women in particular can benefit from the muscle strengthening offered by the Core Program.
Hormones affect joint laxity, too. Women have looser ligaments than men, which are even looser during ovulation. The fact that women have looser ligaments means that women's joints are more flexible than those of men; it also means they have to rely more on muscle strength to keep their joints in good alignment. Having stronger muscles will make for more stable joints, which means both fewer injuries and greater ease of motion.
Other hormone-related differences between men and women relate directly to their reproductive systems. The Core Program exercises will enhance the health and well-being of a woman's reproductive system in several ways: They will help strengthen muscles that have to bear the additional weight of pregnancy, and will relieve back and foot pain stemming from already weak and imbalanced muscles that are further strained by pregnancy. The exercises will also strengthen the pelvic muscles so important in childbirth thereby making labor and delivery easier.
The hormonal changes that occur in women over the course of the life cycle also point to the need for the Core Program. For example, while estrogen may not do much for muscles, it's terrific for bones (and not to mention hearts!). Using exercise to maximize the benefits of estrogen during the menstruating years will mean that you have maximum amounts of bone mass to draw upon when menopause begins, bringing with it a decrease in estrogen levels, which in turn leads to an acceleration of bone loss and a higher risk of osteoporosis.
Another common effect of the estrogen depletion that occurs at menopause is that the muscles of the pelvic floor, which are responsible for supporting the function of the bladder, vagina and rectum, lose what is called their "fluffiness," which is another way of saying their tone or elasticity. If the muscles of the pelvic floor don't maintain their tone, urinary incontinence problems, as well as decreased sexual satisfaction, can be the result.
The Core Program will help reinforce the benefits of estrogen and counteract many of the deficits that may occur when estrogen levels fall at menopause. The core exercises will: help optimize the bone-building that continues to occur from birth until women reach their mid-twenties, so that they'll have a plentiful supply of bone to draw upon in later years; maintain that bone density until age 35, which is when most women begin losing more bone than they are able to build; and will put the brakes on the acceleration of bone loss that occurs at menopause and during the years afterward.
The Core Program also strengthens the muscles of the pelvic poor, which will help women at all stages of life. Research is beginning to look at the possible connection between ovulation and the incidence of knee injury. With the number of young female athletes increasing all the time, definitive studies need to be done. However, a study published in the Journal of Orthopedic Research reported a fascinating finding. Researchers in California observed forty women with ACL (anterior cruciate ligament) knee tears. They found that a high number of their subjects suffered their injuries during the ovulation phase of their menstrual cycles. This phase is marked by a significant rise in estrogen, as well as another hormone called relaxin. Ligaments, the ropelike structures that stabilize joints by attaching bones-to-bones, tend to be looser in women than in men. During ovulation, the hormones cause ligaments to relax even more. Because the ligaments may become too loose to maintain the stability of the joint, they become more vulnerable to tearing. And, unlike muscles, ligaments can't be changed through exercise.
Excerpted with permission from The Core Program: 15 Minutes a Day Can Change Your Life by Peggy W. Brill (Bantam Books; 2001; $24.95; www.randomhouse.com)