Female Athletes

Although similar athletic training regimens and injury
patterns are seen in both male and female athletes, there are many
anatomic and physiologic variations that explain the differences in
mechanics, performance, and injury rates.

Essential body fat, which is the normal fat that is
stored in and nourishes the body’s organs, is 9% to 12% in females and
approximately 3% in males (the significant difference is largely the
result of the fat in breasts and other gender-specific organs). In the
average nonathlete, normal body fat in females is 18% to 24% and is 12%
to 16% in men. Endurance athletes should maintain body fat of 12% to
18%, but this often drops dangerously to 6% to 8% in elite athletes.
However, dropping below a safe level of body fat directly affects the
ability to menstruate, an important component of the female triad.
Greater body fat leaves females more buoyant, a potential advantage in
water sports.

Greater muscle mass per pound of weight explains why
males are stronger, run faster, and jump higher than equally trained
females. In general, when adjusted for body mass, female strength is
approximately two thirds that of males, with their upper body strength
even less matched than lower body strength compared to males. Women
also tend to have greater ligamentous laxity that may contribute to
increased injury patterns, such as multidirectional instability of the
shoulder, patellofemoral dislocations, and ankle instability.

There are several differences in physiology and aerobic
capacity that are important to consider when implementing training
regimens and in achieving realistic athletic goals. The major
physiologic factors that contribute to aerobic differences in females
include smaller body size, greater body fat, lower muscle mass, and
reduced oxygen-carrying capacity. The VO_2max measures the
body’s ability to extract oxygen from the air and deliver it via the
blood to muscle tissue. It is essentially a measure of aerobic
capacity. The average woman has a 15% to 30% lower VO_2max because of several factors:

Females also have a resting metabolic rate that is 5% to
10% lower than males, which affects the ability to lose weight with
training. Because of the aforementioned physiologic differences,
cardiovascular training programs and performance goals for females
should be individualized on the basis of previous athletic experience
and gender.

Hormonal variations throughout the menstrual cycle, as
well as different stages of physiologic maturity, can have an impact on
athletic performance, body composition, bone density, and injuries.
Cyclic endogenous hormones, such as estrogen and progesterone, affect
many physiologic systems in the body such as metabolic,
thermoregulatory, cardiovascular, respiratory, and psychological.
Dysregulation can certainly affect performance and may have an effect
on injury. Several studies have looked at the effect of the menstrual
cycle on performance and injury but the results are varied and mainly
inconclusive. Although there is no definite evidence that a specific
phase of the menstrual cycle increases risk of injury or decreases
performance, one relatively consistent finding is that premenstrual
symptoms can decrease performance and consequently increase risk of
injury. Exogenous hormones, including oral contraceptives, in addition
to decreasing iron deficiency anemia and protecting bone health, are
known to alleviate dysmenorrhea, decrease premenstrual symptoms, and
regulate menses—all of which can be beneficial to the athlete. A few
studies have shown a lower incidence of musculoskeletal injuries with
oral contraceptive use, likely secondary to the alleviation of
premenstrual symptoms and dysmenorrhea.

Growing concerns for women athletes led to the discussion of and need for research investigating the interrelationship between disordered eating, athletic amenorrhea, and premature osteoporosis—the three components of the female athlete triad (Fig. 4-2). The term female athlete triad
was defined at the Triad Consensus Conference in 1992, led by members
of the American College of Sports Medicine. Each component of the triad
occurs on a spectrum of severity and is often interrelated, which can
lead to serious long-term health consequences. However, not all
components of the triad need to occur simultaneously. Diagnosis of one
component of the triad should alert health care providers to be
suspicious about the other components.

Female athletes are often pressured to have and maintain
low body weight and body fat both to enhance performance and/or for
appearance. In their quest to maintain low body weight, they may
succumb to disordered eating, which can cause an imbalance of energy
intake versus energy expenditure. Energy depletion can lead to a
dysregulation of the hypothalamic-pituitary-ovarian (HPO) axis,
resulting in hypoestrogenism or athletic amenorrhea. Subsequently, a
lack of exposure to the hormone estrogen can cause premature bone loss
or osteopenia/osteoporosis. Thus, knowledge of the three components and
how they relate is imperative when treating female athletes.

The prevalence of the female athlete triad is unknown.
There are three groups of sports that have increased risk for
developing the triad:

Although elite athletes are often profiled as the
classic example of being high risk for developing the triad, it can
occur in any physically active female.

The first component of the triad, disordered eating, can
range from simple restriction of food intake, to occasional binging and
purging to laxative and/or diuretic abuse, or to frank anorexia nervosa
and/or bulimia nervosa. The majority of females affected with the triad
do not fit the Diagnostic and Statistical Manual of Mental Diseases,
4th edition (DSM IV) criteria of anorexia or bulimia, but may fit into
a more broad diagnosis of eating disorder not otherwise specified
(EDNOS) (Box 4-1). Studies lack consistent and
valid diagnostic instruments for the assessment of disordered eating
and thus prevalence studies may not be accurate. Up to 62% of female
college athletes have some degree of pathologic weight control
behavior. There are several instruments, such as the Eating Attitudes
Tests and Eating Disorders Inventory, that attempt to document the
existence and/or risk of eating disorders, but most instruments are
blatant in what they are searching for and athletes may hide their
signs and symptoms, thus skewing the results.

Predisposing factors for disordered eating are
multifactorial and often stem from low self-esteem. The athletes often
have body image disturbances. The pressures of adolescence, puberty,
and competition may lead these athletes to find comfort in a false
sense of control with their eating and exercise patterns. Biologic,
psychologic, and social factors all contribute to predisposing risk. A
history of family dysfunction, physical or sexual abuse, perfectionism,
and/or long-term chronic dieting are often found in females who display
signs of eating disorders. Traumatic events—such

as
loss of a family member, friend, or coach—change in competitive
environment (i.e., high school to college and college to professional
world transitions), and acute or chronic injuries can often escalate
the severity of their disordered eating and lead to greater health
consequences. A list of signs and symptoms of disordered eating is
given in Box 4-2, and complications are given in Box 4-3.
Disordered eating can severely affect athletic and academic
performances. The negative energy balance created can decrease
endurance, strength, speed, reaction time, and concentration—all of
which increase the risk of sports-related injuries. Prolonged
insufficient caloric consumption can lead to significant medical and
psychological consequences such as depression and cardiovascular,
endocrine, thermoregulatory, and gastrointestinal complications.

Disordered eating sets the stage for a negative energy
balance. Restricting calories, along with intense training schedules,
leads to a severe energy deficit that affects the HPO axis. This
affects the menstrual cycle and can lead to the second component of the
triad, athletic amenorrhea.

The prevalence of amenorrhea in the general population
is 2% to 5%, but several studies have shown the prevalence in female
athletes may be as high as 66%. The combined effect of poor nutrition
and intense training regimens, leading to significant caloric deficits,
disrupts the reproduction function by suppressing the HPO axis. This is
currently the leading hypothesis in the mechanism of athletic
amenorrhea. There is a decrease in the pulse frequency of
gonadotropin-releasing hormone from the hypothalamus, which leads to
dysfunction in the secretion of luteinizing hormone and
follicle-stimulating hormone from the pituitary gland. Luteinizing
hormone suppression leads to ovarian suppression and anovulation,
resulting in amenorrhea.

Menstrual irregularity, similar to disordered eating,
has a continuum of disturbances. The dysfunctions range from
luteal-phase deficiency to anovulation, oligomenorrhea, and
hypoestrogenemic amenorrhea. There are two forms of amenorrhea: primary
and secondary. Primary amenorrhea is when menarche has not occurred by age 16. In this form, the reproductive axis has not yet coordinated to produce a

menstrual period. The main contributing factor to primary amenorrhea is
the age at which intense training is begun. The earlier the athlete
begins intense training, the greater the risk of primary amenorrhea. Secondary amenorrhea
is when menses is halted for three or more consecutive months after the
reproductive axis has previously produced at least one menstrual period.

Disordered eating and athletic amenorrhea are
significant potential precursors to early osteoporosis or osteopenia.
Osteoporosis or osteopenia is the third component of the female athlete
triad. Osteoporosis is defined as bone mineral density (BMD) measured
by a dual-energy x-ray absorptiometry scan (DEXA), greater than 2.5
standard deviations below that of a young, healthy, Caucasian, adult
female (or a T score at or below -2.5). Osteopenia is defined as 1 to
2.5 standard deviations below a normal adult (or a T score of – 1 to –
2.5). Alteration of bone homeostasis (bone formation and bone
resorption) leads to decreased bone mineralization and low bone
density. Estrogen plays a significant role in bone homeostasis.
Estrogen receptors are found in osteoblasts and osteocytes and slow the
resorption of bone by decreasing osteoclastic resorption. Estrogen also
alters the renal handling of and gastrointestinal absorption of
calcium, which is critical for osteoblastic function and bone building.
Young athletes with primary or secondary amenorrhea lack the estrogen
necessary to achieve peak bone mineral density.

Ninety percent of bone mineral content is accrued by the
end of adolescence. Typically, a young, adolescent, eumenorrheic female
with good nutrition will gain 2% to 4% bone mass a year. A chronically
estrogen-depleted state like athletic amenorrhea can cause a 2% loss of
bone mass a year. Young athletes with intense training patterns and a
negative caloric balance are at increased risk of skeletal fragility.
This is of concern, not only for fractures and stress fractures during
their current sports and training, but leaves them at tremendous risk
for hip, wrist, and spine fractures later in life.

Several studies have investigated the relationship
between reproductive function and bone density. Most of these studies
have shown significant increased risk of fracture in those athletes
with menstrual dysfunction. In fact, one study by Barrow et al. found
that almost half of the college female long-distance runners with
irregular menses had at one point reported a history of stress fracture.

Although return of menses can halt the process of bone
resorption in adolescence, it does not reverse the damage that has
already been done. The treatment of amenorrhea with estrogen
replacement therapies may restore bone homeostasis at that point in
time but does not make up for the prior imbalance; thus, these young
athletes will never reach their potential peak BMD. Exogenous estrogen
only normalizes the rate of resorption; it does not have a direct
effect on bone formation.

At this time, pharmacologic treatment of
osteopenia/osteoporosis in female athletes is not well studied.
Bisphosphonates such as alendronate, used in postmenopausal women, are
not recommended for premenopausal women of childbearing age as a result
of their teratogenic effects. The selective estrogen reception
modulator class of agents, such as raloxifene and tamoxifen, are also
indicated for postmenopausal women but are not approved for
premenopausal women. There is currently no pharmacologic treatment for
osteopenia or osteoporosis that is approved by the U.S. Food and Drug
Administration for premenopausal women. Treatment of the athlete with
signs of osteopenia or osteoporosis consists of restoring menses,
improving nutrition, having an intake of 1,500 mg of calcium/day and
performing weight-bearing exercises.

The female athlete triad may potentially affect all
female athletes. The three components are interrelated, and the
presence of one of the components should raise suspicion for the others.

Stress fractures are partial or complete breaks in the
architecture of bone. These fractures occur as a result of the
inability of bone to sufficiently remodel after exposure to repetitive
overload. The diagnosis of a stress fracture can often be made on the
basis of history and physical examination. Patients will often report a
recent increase in training regimen (either intensity or duration) over
a short period of time. Running is the most common activity that leads
to stress fractures, but any sport that requires repetitive impact
loading can lead to stress fractures.

The vast majority of the literature has found that
stress fractures are more common in female athletes and military
recruits when compared with their male counterparts. In a

recent
study of college athletes, stress fractures were significantly more
common in women. The fractures occurred most commonly in track and
cross-country athletes. Soccer was the only sport where the incidence
of stress fractures was higher in males. In women, the foot was the
most common anatomic region to be involved, but the tibia and the
femur, respectively, were the most common bones to be involved. In men,
the ankle was the most predominant anatomic site, followed by the foot
and the tibia.

Many predisposing risk factors for stress fractures in
the female athlete have been studied, such as age, gender, skeletal
alignment, low bone density, hormonal factors, training parameters, and
footwear. Risk factors for stress factors in female track-and-field
athletes include significantly older age at menarche, a history of
irregular menses, and restrictive eating patterns and dieting—all
factors that reduce bone density. A high longitudinal arch, leg length
discrepancy, and excessive forefoot varus have all been associated with
increased risk of recurrent stress fractures, with the tibia being the
most common location. There is an increased risk of pubic ramus
fractures in integrated military training, presumably because of
increased stride length set by males during marching.

ACL injuries in female athletes are 3 to 10 times more
common than in males. The mechanism of injury is most commonly
noncontact during deceleration, landing, or cutting. The “at-risk”
position of the leg is with knee extended, hip adducted and internally
rotated, and leg externaly rotated. Once a valgus moment is produced
with the leg in the aforementioned position, the ACL is at significant
risk. Soccer, basketball, field hockey, lacrosse, and skiing appear to
be the sports with the greatest risk.

The risk factors for ACL injury have been divided into two groups:

Anatomically, in females, an increased Q-angle, genu recurvatum, genu valgum, hip varus, pelvic width, and foot

pronation have been implicated as contributing factors. The femoral
notch size has also been implicated as a risk factor for noncontact ACL
injury. Currently, anatomic factors identified in the literature
include a notch width in patients with bilateral ACL tears that is less
than in patients with unilateral tears. Notch width is smaller in
females than males (see Fig. 4-1),
and the notch width index (condylar width to notch width) in females is
less than males. Some researchers have suggested that increased laxity,
especially in patients with recurvatum, may contribute to the increased
incidence. The increased laxity may contribute to diminished joint
proprioception, causing the knee to be less sensitive to potential
damaging forces.

Data on the hormonal differences between men and women
as a cause of ACL injury are somewhat controversial. Some studies have
suggested an increased incidence of ACL injuries during the estrogen
surge at midcycle, whereas others report an increase around the time of
menses. The use of oral contraceptives has also been investigated to
try to understand hormonal influences but no definitive conclusions can
be made at the present time.

Uhorchak et al. performed a
prospective study looking at risk factors associated with noncontact
ACL injuries. In women, narrow notch width, generalized joint laxity,
and increased body mass index were all significant risk factors. There
was a trend toward significance for knee laxity on KT-2000 testing. In
these military recruits, the presence of one of these factors led to a
relative risk 2.7 to 4 times those without risk factors. Using a
regression model, including femoral notch width, body mass index, and
generalized joint laxity, the authors were able to predict 75% of the
ACL injuries.

Although it may be difficult to control potential
intrinsic risk factors, changes can be made to influence potential
extrinsic causes. Knee joint position during landing, landing forces,
and cutting maneuvers have been implicated as potential risk factors (Fig. 4-5).
Most studies report that females tend to land with the knee and hip in
a more extended position. When landing with the knee in a position of
extension, females tend to recruit the quadriceps eccentrically to a
greater degree than the hamstrings. Research has also shown with low
knee flexion angles, the maximal force generated by the quadriceps
exceeds the tensile strength of the ACL. Females have also been shown
to have less gluteus medius activation than in males. This is important
because hip motion influences knee motion. A recent study in female
athletes showed that the knee abduction angle at landing was 8 degrees
greater, and the knee flexion angle at

landing
was 10 degrees lower in the ACL injured than uninjured athletes. They
concluded from their study that decreased neuromuscular control
(increased dynamic valgus and knee abduction moments) were risk factors
for ACL injury, with 73% specificity and 78% sensitivity.

Although many athletes may possess adequate strength in
the gym during isolated exercises, many cannot translate isolated
muscle strength into coordinated skilled movement. As a result, there
have been many neuromuscular training prevention programs developed to
decrease the incidence of ACL injury and all with great success. For
example, Sportsmetrics is a three-part prevention program focusing on
flexibility, strengthening, and plyometrics. During phase I, proper
jumping techniques are taught. Phase II concentrates on building
strength and agility, and phase III focuses on achieving maximal
vertical height. Data from their studies have shown a decrease
incidence of ACL injuries. The program itself was found to decrease
peak landing forces, decrease varus and valgus motion with landing, and
increase hamstring strength, thus improving hamstring-toquadriceps peak
torque ratio. Another program is the California ACL Prevention Project:
Prevent Injury and Enhance Performance PEP Program. The program has
five components (avoidance, flexibility, strengthening, plyometrics,
and agilities) that are performed 2 to 3 times weekly. Randomized
controlled trials using this program have shown significant decreases
in ACL injuries, noncontact ACL injuries, and practice ACL injuries.

Few studies have specifically addressed outcomes for
female ACL reconstructed athletes. Controversy exists in the literature
regarding outcomes of ACL reconstruction when comparing men versus
women. Although some studies have suggested higher clinical failure
rates in women, other researchers have not found significant
differences. Currently, most authors agree that gender alone should not
be used as selection criteria for ACL reconstruction. In terms of graft
selection, many surgeons have shown a trend in using hamstring grafts
for women as a result of improved cosmesis and minimizing graft site
morbidity. However, reduced peak torque of the hamstring muscles has
been reported, and concern exists over a tendency toward
postreconstruction residual laxity and tunnel widening. Barrett et al.
performed a prospective review comparing hamstring and patellar tendon
ACL reconstruction in female patients. Although not statistically
significant, there was a trend toward a greater failure rate and
increased laxity on physical examination and KT-1000 arthrometer
differences. In the hamstring group, there was a significant increase
in pain compared with the

patellar
tendon group. In a case-control comparison of hamstring versus bone
patellar tendon bone in female athletes, no functional differences were
seen between the two groups. However, there was significantly greater
kneeling avoidance, numbness/dysesthesia, and loss of passive extension
in the bone-patellar tendon-bone group. The authors concluded that
hamstrings were an acceptable graft alternative in the female athlete.

Because the incidence of ACL injuries is more common in
women and there are increasing numbers of female athletic participants,
future research needs to focus on appropriate prevention and treatment.

Most of the research on exercise during pregnancy
suggests that it is beneficial, but physiological parameters must be
monitored, and limitations must be applied individually. The goals
throughout pregnancy should be to maintain or improve preexisting
levels of fitness without risk to the mother or the developing fetus.
Exercise in the supine position should be avoided because of potential
risk to the great vessels from gravity acting on the uterus.

Studies have shown improvements in well-being and body
image, avoidance of excessive weight gain, decreases in musculoskeletal
complaints (back pain), improved labor symptoms, and facilitation of
postpartum recovery. Potential risks include environmental exposure,
dehydration, hypoxia, and uterine trauma. Hot and humid environments
should be avoided for risk of dehydration. A meta-analysis was
performed in 1992 to help determine safe exercise recommendations
during pregnancy. After analyzing the 18 studies involved, the authors
concluded that pregnant women can exercise safely three times a week
for 43 minutes at a heart rate of 144 beats per minute. In 1994, the
American College of Obstetrics and Gynecology published revised
guidelines for exercise pregnancy (Box 4-4).
Thus, exercise during pregnancy can have many potential benefits, if
appropriate caution is observed and certain restrictions are used.