Dose-response relationships between energy availability and bone turnover in young exercising women

Weight-bearing, aerobic exercise increases markers of bone formation during short-term weight loss in overweight and obese men and women

We investigated the impact of weight-bearing, aerobic exercise- and diet-induced weight loss on markers of bone turnover during a larger study of changes in metabolic fitness during short-term weight reduction using a repeated-measures, within-subject experimental design. Subjects (N = 19) underwent 6 weeks of energy restriction (reduced by approximately 3140 kJ/d) and aerobic exercise ( approximately 1675 kJ/d, walking or jogging at 60% maximum oxygen consumption) to induce a 5% reduction in body weight. Bone turnover markers and hormones were measured in serum collected at baseline and after 6 weeks of weight loss. Despite a 5% reduction in body weight at week 6, markers of bone formation, osteocalcin, and bone alkaline phosphatase, were significantly increased, and resorption markers, C-terminal cross-links of type I collagen and soluble receptor activator of nuclear factor kappaB ligand, were unchanged after 6 weeks of energy restriction and exercise. The concentration of leptin was significantly reduced after weight loss, but insulin-like growth factor I (IGF-I) and cortisol levels were unaffected. In conclusion, weight-bearing, aerobic exercise training may favorably affect the balance between bone resorption and formation during weight loss.

Stress fractures: pathophysiology, epidemiology, and risk factors

A stress fracture represents the inability of the skeleton to withstand repetitive bouts of mechanical loading, which results in structural fatigue and resultant signs and symptoms of localized pain and tenderness. To prevent stress fractures, an appreciation of their risk factors is required. These are typically grouped into extrinsic and intrinsic risk factors. Extrinsic risk factors for stress fractures are those in the environment or external to the individual, including the type of activity and factors involving training, equipment, and the environment. Intrinsic risk factors for stress fractures refer to characteristics within the individual, including skeletal, muscle, joint, and biomechanical factors, as well as physical fitness and gender. This article discusses these extrinsic and intrinsic risk factors, as well as the pathophysiology and epidemiology of stress fractures.

Food attitudes in female athletes: Association with menstrualcycle length

The aim of this study was to examine the relationship between indicators of risk of disordered eating, body image and varied menstrual cycle lengths. Altogether, 151 female athletes were invited from 16 sports and 70 female non-athletic controls were recruited from a university lecture class. The participants completed several surveys, including demographics, menstrual cycle history, physical activity, Eating Disorder Inventory (EDI) and the Three Factor Eating Questionnaire (TFEQ). Selected EDI subscales were summed to reflect eating disorder risk and body image. Menstrual cyclicity was based on self-reported cycle length for the last 6 months (normal cycles = 26-32 days, irregular cycles < or =26 or >32 days). Athletes overall had more irregular cycles (29.1%) than the non-athletes (15.7%) (P < 0.05). There were significant differences in scores for eating disorder risk, body dissatisfaction, drive for thinness, cognitive restraint (TFEQ) and disinhibition (TFEQ), only when athletes were divided based on menstrual cyclicity (i.e. irregularly cycling athletes had higher scores than athletes with normal menstrual cycle lengths). No differences in these scores were found between non-athletes with normal or irregular menstrual cycle lengths. In conclusion, irregularly short or long menstrual cycle length is associated with subtle indications of higher risk of disordered eating in female athletes.

The pathophysiology of stress fractures

Stress fractures can occur in any active individual, from the weekend warrior to the elite athlete. As these injuries occur, it is important to understand how bones respond to the stresses placed on them. The understanding of potential intrinsic and extrinsic causes is important in treatment of these injuries. The proper identification and prevention of these stress injuries allows for athletes to return to activity expeditiously.

Practical use of the International Olympic Committee Medical Commission Position Stand on the Female Athlete Triad: a case example

The female athlete triad consists of the interrelated problems of disordered eating, amenorrhea, and osteoporosis, and it is believed to affect female athletes in all sports and at all levels of competition.

OBJECTIVE

The current article highlights the Position Stand on the Female Athlete Triad of the International Olympic Committee's Medical Commission (IOCMC).

METHOD

The literature related to disordered eating, energy availability, amenorrhea, and bone loss in athletes is briefly reviewed. A hypothetical case is presented to illustrate some of the common issues and problems encountered when working with athletes affected by the triad, such as the effect of weight on performance in "thin" sports, coach involvement, sport participation by symptomatic athletes, and treatment resistance/motivation.

RESULTS

Strategies recommended by the position stand for managing those issues and problems are presented regarding the referral, evaluation, and treatment phases of the management process.

CONCLUSION

Implications of the position stand are discussed in terms of the IOCMC's endorsement of the athlete's health being primary to her performance.

Menstrual disorders in athletes

The various menstrual disorders in athletes may reflect different degrees of exposure to a disrupting factor or differences in the susceptibility of various women to disruption. The incidences of these disorders are not well documented, but they appear to be highest in aesthetic, endurance and weight-class sports, and at younger ages, higher training volumes and lower bodyweights. The morbid effects of these disorders include infertility, low bone mass, impaired endothelium-dependent vasodilation, and impaired skeletal muscle oxidative metabolism. The high incidences of menstrual disorders in athletes may derive in part from the self-selection of extraneously affected women into athletics, but many women acquire their menstrual disorders in athletics by failing to adequately increase dietary energy intake in compensation for exercise energy expenditure. Applied research is needed to develop effective dietary interventions that are acceptable to athletes.

Biomedical Research on Health and Performance of Military Women: Accomplishments of the Defense Women's Health Research Program (DWHRP)

In 1994, Congress provided dollar 40 M for biomedical research on issues of importance for military women. This supported 104 intramural and 30 extramural studies and launched an era of research to narrow the knowledge gap on protection and enhancement of health and performance of military women. Projects addressed issues specific to female physiology (e.g., gynecological health in the field, maternal malaria), problems with higher prevalence for women (e.g., marginal iron deficiency, stress fracture), and issues of drug and materiel safety that had only been extrapolated from studies of men (e.g., chemical agent prophylaxis, fatigue countermeasures). Several important assumptions about female physiology and occupational risks were found to be astoundingly wrong. Hormonal changes through the menstrual cycle were less important to acute health risks and performance than predicted, exercise did not increase risk for amenorrhea and consequent bone mineral loss, and women tolerated G-forces and could be as safe as men in the cockpit if their equipment was designed for normal size and strength ranges. Data on personal readiness issues, such as body fat, physical fitness, nutrition, and postpartum return to duty, allowed reconsideration of standards that were gender appropriate and not simply disconnected adjustments to existing male standards. Other discoveries directly benefited men as well as women, including development of medical surveillance databases, identification of task strength demands jeopardizing safety and performance, and greater understanding of the effects of psychosocial stress on health and performance. This surge of research has translated into advances for the welfare of service women and the readiness of the entire force; relevant gender issues are now routine considerations for researchers and equipment developers, and some key remaining research gaps of special importance to military women continue to be investigated.

Stress Fractures and Knee Injuries in Runners

Running often can cause injuries to the knee as a result of kinetic chain dysfunctions. Addressing these dysfunctions in rehabilitation can prevent future injury. Stress fractures often occur in runners who engage in training errors. Female runners are particularly susceptible to stress fractures, especially in the setting of the female athlete triad. Proper identification and prevention of these injuries allows for athletes to return to running expeditiously.