From the HSS Manual of Rheumatology and Outpatient Orthopedic Disorders
Regular exercise has been shown to decrease the risk for multiple diseases, including coronary heart disease, hypertension, osteoporosis, obesity, depression, and some reproductive cancers. The U.S. Preventive Services Task Force and the Office of Disease Prevention and Health Promotion have emphasized that as the population ages (with women comprising the majority of the elderly), physical activity and fitness must be viewed as a health goal priority.
Additionally, studies have demonstrated that girls who play high school sports are less likely to have an unwanted pregnancy or use drugs, are more likely to graduate from high school and have lower levels of depression. Clearly, encouraging an active life-style among women is critical to the long-term health of our country.
Although many aspects of physical activity are similar in both male and female populations, some issues require special consideration in the female athlete.
- Body Structure
- Skeletal growth reaches its peak at an earlier age in girls (10.5 to 13 years of age) than in boys (12.5 to 15 years of age). Skeletal maturity occurs by age 17 to 19 in girls, and by age 21 to 22 in boys.
- The female pelvis is wider than the male pelvis, causing an increased quadriceps (Q) angle, which commonly contributes to anterior knee pain (also called patellofemoral syndrome).
- Women develop thinner, lighter bones than their male counterparts, which may predispose them to osteoporosis and stress fractures.
- Body Composition
- In general, women have approximately 10% more body fat than men do, and 60% to 85% of the total muscle cross-sectional area of men. Because muscle is more metabolically active than fat, women have on average a resting metabolic rate 5% to 10% lower than that of men.
- In response to weight-training, women experience similar relative increases in strength as in men. Because muscle hypertrophy depends on hormones as well as training program type and volume, levels vary per athlete. However, male athletes have greater absolute strength and muscle hypertrophy (due to their hormonal environment) than female. Even with training, females have 30% to 50% less upper body strength than males.
- The percentage of body fat can be estimated by a variety of methods; ideal body fat composition varies with age and sex. Efforts have been made to establish a healthy minimum body fat percentage but factors vary in women. However, athletes with a body fat percentage below 15% should be examined for any indications of the female athlete triad.
- Cardiorespiratory System
- Women have a smaller thoracic cage and heart size, resulting in lower lung capacity and maximal cardiac output.
- Maximum oxygen composition (VO2 max) is lower in women, largely because of differences in body composition and oxygen-carrying capacity. VO2 max is similar in boys and girls before puberty.
- Circulatory System
- Women have a smaller blood volume, smaller iron stores, and lower concentrations of hemoglobin. These factors are associated with a lower oxygen-carrying capacity and also increase the risk for anemia.
- Both male and female elite athletes tend to have lower levels of hemoglobin than their sedentary counterparts. This may be secondary to both a low dietary intake and exercise-related blood loss, such as occurs from the gastrointestinal tract.
- Endocrine System
- There is no evidence that the phase of the menstrual cycle influences athletic performance.
- Female athletes may experience a wide array of alterations in the menstrual cycle, ranging from suppression of the luteal phase to amenorrhea. The latter is especially prevalent in athletes at risk for the “female athlete triad” (see Section II).
- Pregnancy results in many physiologic changes, including increases cardiac output, blood volume and oxygen demand. The American College of Obstetrics and Gynecology recently revised guidelines regarding exercise and pregnancy. ACOG indicated that recreational and competitive female athletes with uncomplicated pregnancies can remain active but those who exercise strenuously should seek close medical supervision. Athletes with a history of or risk for preterm labor or fetal growth restriction are advised to reduce activity in the second and third trimesters. Recent research also indicates that certain types of activities should be limited and/or avoided during pregnancy, such as diving (due to changes in pressure underwater), exercise in the supine position (due to restriction in large blood vessels) and any activity associated with risk for blunt abdominal trauma (contact sports, skiing).
THE FEMALE ATHLETE TRIAD
- General Considerations
- The female athlete triad refers to the interrelatedness of three conditions: disordered eating, amenorrhea, and osteoporosis.
- Traditionally, female athletes at risk were thought to be those whose activity emphasized leanness for aesthetic reasons (ballet, gymnastics), who associated low body weight with improved performance (distance running), or those who were classified by weight (rowing, judo). However, women at risk have been found in many other sports, including swimming, soccer, volleyball and cycling, and also in health clubs.
- Disordered Eating
- It is important that the clinician differentiates disordered eating from the eating disorders of anorexia nervosa and bulimia nervosa, which are psychiatric diagnoses with specific diagnostic criteria. Disordered eating is a much more common phenomenon, and restricting awareness to the extremes of anorexia and bulimia will result in failure to recognize girls at risk for the triad.
- Disordered eating behaviors include:
- Food restriction
- Fasting/skipping meals
- Binging (which may or may not be followed by purging)
- Use of diet pills, diuretics and laxatives
- Girls suffering from disordered eating are often:
- Preoccupied by thoughts of food
- Plagued by distorted body image
- Afraid that any weight gain is the equivalent of “getting fat”
- Feel guilt about eating either before/after meals
- Compulsive exercisers
- Primary amenorrhea is defined as the absence of menarche by the age of 16.
- Secondary amenorrhea is the absence of three to six consecutive menstrual cycles in women who have experienced menarche.
- It is believed that exercise in the setting of inadequate calorie consumption may contribute to an “energy-deficient” state, which may lead to amenorrhea.
- In this setting, amenorrhea represents a hypoestrogenic state, which can predispose to osteoporosis.
- Exercise-related amenorrhea is a diagnosis of exclusion. Other causes of amenorrhea, such as pregnancy, must be considered before it is assumed that cessation of menses in an athlete is exercise-driven.
- Osteoporosis refers to bone loss in addition to inadequate bone formation, which results in lower bone mass, increased skeletal frailty, and increased risk of fracture.
- Premature osteoporosis occurring in the female athlete may be irreversible, even when treated with calcium supplementation, hormonal replacement therapy, and correction of amenorrhea.
- Pharmacologic treatment of osteoporosis in the premenopausal female athlete is difficult. Bisphosphonates, which are indicated for postmenopausal women, have not been well studied in the premenopausal population or in pregnancy. Although some physicians treat the amenorrhea and osteoporosis of the female athlete triad with oral contraceptive pills, such treatment has not been shown to actually improve bone density and mineralization.
- Stress fractures may occur with more frequency and severity in female athletes at risk for the triad; although there are no current guidelines regarding screening, one should consider evaluation of bone density to screen for premature osteoporosis in an athlete identified as being at risk for the female athlete triad.
Current knowledge suggests that most injuries sustained by athletes are sport-specific rather than gender-specific (see Chapter 22). However, several orthopedic issues of special concern in the female athlete deserve specific mention.
- Anterior cruciate ligament (ACL) injuries
- Epidemiologic data suggests that the incidence of severe knee injuries, especially ACL injuries, is higher in women than in men, particularly in the sports of soccer, basketball, and lacrosse (threefold to fivefold increase).
- The causes of increased ACL injuries are unclear. Factors thought to contribute to the higher rate of ACL injury are both intrinsic and extrinsic.
- Intrinsic factors
- Ligament size
- Intercondylar notch dimensions
- Muscular strength and coordination
- Limb alignment
- Hormonal influences
- Extrinsic factors
- Shoe-floor interface
- Level of skill and experience
- Inadequate training and coaching
- There is data to suggest that women are more likely to tear their ACL during the first half of the menstrual cycle. The explanation for this observed difference in incidence in unclear, but may be related to neuromuscular and proprioceptive functions.
- There exist programs designed to decrease non-contact ACL injury risk which have demonstrated a significant decrease in the incidence of injury in both high school and collegiate athletes. The common factors in these training programs include balance, strength, proprioception and plyometric training. The best characterized and studied programs are the Sportsmetrix and PEP programs.
- Patellofemoral Pain
- Injuries to the patellofemoral joint are more common in women. Patellofemoral pain is often thought to be secondary to a variation in limb alignment (“miserable malalignment syndrome”) consisting of a combination of increased anteversion of the femoral head, internal rotation of the femur, external rotation of the tibia, and foot pronation. Other anatomic features often blamed for patellofemoral pain include an increased quadriceps angle and hypermobility of the patella.
- Patellofemoral pain should be differentiated according to whether the patella is hypermobile or “tight” (lateral patella compression syndrome). This distinction is important because treatment varies depending on whether the patella needs to be restrained (in the case of hypermobility) or “loosened” (in the case of tight lateral structures causing lateral compressive pain.). In the case of the hypermobile patella, strengthening of the medial quadriceps (vastus medialis obliquus) aids in restraining the patella. In the patient with tight lateral structures causing lateral pull of the patella, stretching lateral structures, including the lateral retinaculum and iliotibial band, is recommended. A patellar tracking brace may be helpful in the patient with hypermobility of the patella but may actually exacerbate pain in the patient with lateral patella compression syndrome.
- Shoulder Pain
- Adhesive capsulitis is an idiopathic inflammatory synovitis in the glenohumeral joint. It occurs three to seven times more frequently in women than in men. The cause is not well understood, but the clinical entity is frequently associated with other conditions, such as diabetes, hypothyroidism, trauma and menopause. Four distinct stages have been recognized, which reflect the degree of synovitis. The cornerstones of treatment include intraarticular steroid injection and a rehabilitation program to maintain strength and range of motion. Manipulation under anesthesia and arthroscopy may be required.
- Impingement syndrome, an overuse injury to the rotator cuff, occurs frequently in both male and female patients. However, in women, causative factors are often related to underlying glenohumeral laxity. Increased capsular laxity requires an increase in rotator cuff activity, leading to overuse and impingement. Another factor, especially in the novice female athlete, is deconditioning and weakness of the upper extremity, which leads to rapid fatigue of the rotator cuff, particularly with overhead activity.
- Stress Fractures
- Although stress fractures occur in both male and female athletes, they are clinically considered more common in female athletes, especially in certain sports such as running and gymnastics. The risk for stress fractures is clearly greater in women than men, but there is great variability in reporting of incidents. Studies indicate a range of increased risk from 1.5 to 13 times greater in women than in men.
- The tibia is the most common site of stress fracture for all athletes; stress fractures of the pelvis, femur and metatarsals are reported more frequently in female athletes.
- Spondylolysis (secondary to stress fracture) and spondylolisthesis should be considered in athletes complaining of low back pain who perform repetitive flexion and extension activities.
- Variables related to the increased rate of stress fractures in women include the following:
- Menstrual irregularity/amenorrhea
- Low bone mineral density & bone size
- Training errors
- Inadequate shoes/equipment
- Biomechanical alignment of the lower extremity
- Decreased muscle strength in the lower extremity
- Diet /nutrition
- Evaluation of the female athlete with a stress fracture must include a careful menstrual history; loss of menses or any change in frequency or duration of the menstrual cycle requires further evaluation.
Achieving fitness through moderate exercise has been linked to lower risks of heart disease, hypertension, cancer, depression, and osteoporosis---diseases that affect both women and men. General guidelines suggest that both women and men should be evaluated by a physician before embarking on an exercise program, especially after age 40. Although most medical considerations in the athlete are not gender-specific, a few issues are of special concern to those caring for the female athlete.
- Osteoporosis. Moderate exercise may help to decrease the risk of osteoporosis, but exercise in the face of disordered eating and amenorrhea may contribute to premature osteoporosis. Low estrogen states are associated with an increase in urinary loss of calcium and a decrease in calcium absorption from the gastrointestinal tract, which lead to less calcium deposition in bone. In the female athlete, a stress fracture may be a warning sign of osteoporosis and warrants thorough evaluation. Additionally, illnesses such as hyperthyroidism (whether overt, subclinical, or iatrogenically – induced by excessive replacement of thyroid hormone) are more common in the female population and may contribute to osteoporosis.
- Rheumatologic Disease. Most rheumatologic diseases, such as lupus, rheumatoid arthritis, and fibromyalgia, are reported to occur two to ten times more frequently in women than in men. Often, the first manifestation of such an illness is mistaken for an athletic injury. The physician should be alert to this fact and should include rheumatologic disease in the differential diagnosis of musculoskeletal pain, especially in women. RA and SLE are systemic inflammatory disorders and the inflammatory and immunologic processes that are active lead to premature atherosclerosis and osteoporosis. These problems, above and beyond the musculoskeletal and visceral manifestations of these disorders, can cause additive bone, organ and tissue damage and dysfunction.
- Cardiovascular Issues
- Factors affecting the risk for sudden death include the following:
- Age and, to a small degree, cholesterol level (both sexes)
- Hematocrit, vital capacity, and glucose level (women only)
- In women, the incidence of false-positive findings on electrocardiographic exercise testing is much higher than in men; therefore, the use of additional imaging modalities is especially important in the female athlete suspected of having cardiovascular disease.
- Exercise-related anemias. Anemia is more common in the female than in the male athlete, and in fact is more common in the female athlete than in the general population.
- Dilutional pseudo-anemia is a physiologic dilution of hemoglobin that occurs as a result of the increase in plasma volume that is associated with regular exercise. In general, the dilution leads to a hemoglobin drop of 0.5 - 1.0 but may be larger in the most elite athletes. It is often called “sports anemia” and is benign.
- Exertional hemolytic anemia (aka. foot strike hemolysis) has been reported but the exact cause is uncertain. Although initially described in runners, it has since been reported in non-impact sports like swimming. Possible mechanisms include acidosis induced by exercise, turbulence caused by increased output demands, and foot strike.
- Iron deficiency anemia is most common and may be caused by gastrointestinal, sweat, urinary or menstrual losses; impaired absorption, and inadequate intake. This type of anemia has an adverse effect on performance and requires treatment. The CDC recommends iron supplementation for three months.
- Female athletes do not appear to be at greater risk than the general female population for low iron stores. Low ferritin levels without actual anemia also may affect performance. Although no evidence-based recommendation exists, it is common practice to supplement ferritin levels < 20 with iron 325 mg/day; ferritin levels between 20 and 40 are frequently treated with a multivitamin containing iron.
- Infections. Physicians treating female athletes should be aware that certain types of infections, such as urinary tract and vaginal/genital infections, are related to gender and anatomy and therefore are more common in the female population.
Good nutrition is essential to athletic performance, and the basics of good nutrition are not gender-dependent. However, female athletes need to pay particular attention to a few special considerations.
- As mentioned previously, calcium is essential for bone health.
- Recommendations for daily intake (RDI): 1,000 to 1,200 mg in premenopausal women, and 1,500 mg in postmenopausal women and adolescents.
- While calcium supplements are beneficial, many experts believe that intake of calcium-rich foods is a more effective method of meeting calcium RDI.
- See Medical Considerations section IV.
- Iron deficiency is often secondary to inadequate diet in addition to frequent losses, such as through menstruation.
- A thorough evaluation is warranted before iron supplementation is prescribed. When taken with calcium supplements, iron absorption has been shown to significantly decrease. However, vitamin C enhances iron absorption.
- It is unknown whether female athletes have a higher daily iron requirement than current FDA recommendations.
- Protein is essential for muscle development and recovery/repair.
- Female athletes may tend to avoid protein-rich foods for their fat or caloric content to avoid weight gain. Protein deficiencies can create fatigue, cause injury during athletics, and reduce immune system efficiencies.
- Other dietary insufficiencies. Female athletes may have inadequate intake of total calories, protein, fiber and fat in efforts to avoid weight gain. Vegetarian diets often do not contain sufficient nutritional content as well. Such dietary inadequacies are known to contribute to poor bone health and thought to contribute to increased rates of certain injuries and possibly to decreased rate of healing. Extreme restriction of intake may not only affect performance but also have negative effects on health, similar to those seen in the patient with anorexia nervosa.
- Like all athletes, female athletes must maintain appropriate hydration. Athletes can easily lose 2% to 5% of their body water in an intense exercise session. A loss of 2% affects performance.
- Electrolytes (primarily sodium and potassium) lost through exercise can be replaced by adequate diet.
- Female athletes, in an effort to avoid weight gain and/or suppress hunger pains, may drink excessive amounts of water and develop hyponatremia, also called “water intoxication.” The condition is most prevalent in distance runners and triathletes. The result, depletion of the athlete’s blood sodium, can be potentially fatal and symptoms resemble those of other exercise-related disorders. Consumption of sports drinks is a recommended method of prevention.
EQUIPMENT AND SHOES
- Equipment. Only recently has the athletic equipment industry begun to make design exercise equipment intended for use by female athletes. In developing and choosing equipment, the physiologic differences between women and men mentioned briefly at the beginning of this chapter should be kept in mind. These factors should influence the future design of equipment such as bicycles, skis, racquets, and weight machines.
- Shoes. A woman’s foot is different from that of her male counterpart in both shape and size. It is only recently that shoe manufacturers have begun to take such factors into consideration, which has resulted in greatly improved technology that is specific to the female athlete’s anatomy and biomechanics as well as specific to the sport.