Don't stress (your bones) out.

Many dancers (and athletes) discover that sustained, intense physical activity can halt a woman's monthly cycle. While this may strike a busy dancer as more convenient than anything else--no bloating, cramps, or exhaustion crimping your rehearsing and performing--it leads to a greater likelihood of stress fractures.

Estrogen provides a necessary component for bone growth. If you miss periods, you have low estrogen, and that means lower or slower bone development. Bone functions as the major storage area for calcium, which the body needs for essentials such as muscle contractions. When the body lacks enough calcium to perform all of its jobs, it harvests calcium from bone.

The resulting diminishment in bone density leads to greater likelihood of stress fractures. Many studies have shown a clear correlation between a lack of periods, low estrogen, and stress fractures. In dancers, they often occur in the second metatarsal area of the foot, because dancers put pressure on their first and second toes in releve and preparations for jumping. While training can help you land with less impact (use your demi-plie, roll through the foot, etc.), dancers are already at risk for repetitive stress injuries from the daily grind of class, rehearsal, and performance. Add to that a weakened infrastructure, and you have an injury waiting to happen. A dancer's shins are also vulnerable to stress fractures, which will reveal themselves through pain on the involved side while standing or jumping.

Stress fractures, by nature, are hard to diagnose. They tend to occur when a dancer's normal routine gets derailed by a big work load or a new situation. According to Dr. Peter Lavine, a Washington D.C. orthopedist who has worked with the Kirov Ballet, this can happen when dancers are preparing for an audition or performance, or changing to a new school or program. Even when a stress fracture is indicated, X-rays call be negative, therefore a doctor may often decide to order more sophisticated studies, such as a bone scan or MRI. However, Lavine advises that the best treatment is to prevent them in the first place by maintaining a proper calcium intake and by avoiding amennorehea (a loss of menstrual periods).

Stress fractures can be difficult to resolve. A dancer may need to wear an immobilization boot and may miss an entire season. Making prevention a priority" is worth weeks, or even months, of healing. If you have irregular cycles or don't menstruate, don't ignore it. Loss of body fat, an unbalanced diet, and emotional stress can all contribute to amennorehea. Teenagers pay the highest price, especially if they don't begin their cycles until 16 or older. Most people don't develop their full bone mass until they reach 20, and estrogen plays a key role in that development.

One way to restore a regular cycle is to go on a birth control pill, which functions as an estrogen supplement. Some new versions of the pill conveniently only produce a cycle every three months. According to family medicine practitioner Dr. Bill Ross of the Center for Sports Medicine in San Francisco, this doesn't pose a danger to your bones since you are still receiving the needed estrogen supplement.

Make a point of eating to strengthen your bones. Dancers need about 1200mg of calcium per day. Even if you have two servings of yogurt per day, that's only about 700mg. Other high calcium foods include almonds, oysters, and leafy greens--but you'd have to eat a bushel of greens to equal one 500mg mineral tablet. Calcium supplementation needs to be spread out, because the body can only absorb about 500mg at a time. Also be sure to take mineral supplements at night, because you tend to absorb more nutrients during your sleep cycle. Although calcium is the most common mineral known to help bone density, you also need Vitamin D, magnesium, and boron.

You cannot maximize your potential if you neglect your body. Be diligent about your cycle, your diet, and your stress level. If you can keep yourself strong, you can dance well for many years.

Suzanne Martin is principal physical therapist for Smuin Ballet in San Francisco. She also has her own practice in physical therapy and Pilates.