Thursday, August 27, 2009

Injury Risks for the Female Athlete - Part 3

Ok... last section!

Interestingly, repetitive loading sports like distance running are not correlated with higher bone density, although the high impact nature of running would suggest otherwise [11]. This may be due to other factors specific to distance runners, such as the high prevalence of disordered eating or menstrual irregularities. Amenorrhea or other menstrual irregularities are correlated with low bone density, and the risk of a stress fracture in athletes with amenorrhea is almost four times greater than athletes without [23]. It has been hypothesized that estrogen can modify the threshold for damage accumulation of the bone, offering a clue into how menstrual function is linked to bone health. Estrogen may exert its effects on the metabolically active trabecular bone, the porous type of bone found in the spine and all joints. Furthermore, studies have indicated that even without any menstrual dysfunction, energy deficits and disordered eating are related to low BMD and a higher risk of stress fracture [11]. Runners, who commonly have high training volumes and restricted eating patterns, may be at a higher risk of energy deficit than other athletes. Running is also a sport that places immense value on leanness and low body weight, which has independently been found to be a predictor of BMD. Therefore, female athletes with amenorrhea who strive to reach or maintain a low body weight through restrictive eating are at a very high risk for developing stress fractures and osteoporosis later in life. It is crucial that this population in particular be aware of the dangerous and lifelong effects of low bone density.

Although sports like running and gymnastics that emphasize leanness and very low body weight can be dangerous, the majority of Americans are on the opposite end of the weight spectrum. Overweight or obese individuals, while at risk for many other life-threatening conditions like diabetes, heart disease and cancer, have relatively high bone mineral density. Increased body weight is associated with a decreased risk of any type of fracture [22], and has a positive effect on bone turnover and bone density [16]. While not completely understood, the protective effect of higher body weight is possibly due to the increase in skeletal loading (due to more weight on the bones) as well as higher levels of certain hormones like insulin. Weight loss has been found to decrease BMD, but studies suggest that exercise incorporated into a weight loss program may help prevent this bone density decrease. Weight loss through dieting has been repeatedly shown to cause rapid bone loss, but weight loss achieved through exercise alone showed none of these harmful effects. Therefore as obesity is confronted as a nation-wide problem and more people are attempting to lose weight, it is important to consider the impact of the method of weight loss on bone health.

Several nutritional factors are critical in maintaining proper bone health. Calcium is perhaps the most well known mineral to be associated with osteoporosis, and it is true that calcium plays a large role in the disease. If not consumed in the diet, calcium will be leached from the bones, where it forms an integral part of the bone matrix. Other nutritional factors that play a role in bone health are Vitamin D, which must be present for calcium to be absorbed, Vitamin K, phosphorous, potassium, and sodium.

Bone mass can be maintained during adulthood, but there are very few treatments that can reverse bone loss. Current treatments for osteoporosis include estrogen replacement therapy or biphosphonates, which block or slow down the breakdown of bone, or agents like fluoride or parathyroid hormone, which promote the formation of bone [1]. No treatment can “cure” osteoporosis, but some can maintain a sufficient bone mass for normal everyday function and activity.

Overall, women are prone to many of the same exercise-associated injuries as men, such as patellofemoral pain syndrome, iliotibial band friction syndrome, medial tibial stress syndrome, Achilles tendonitis, ACL tears, plantar fasciitis, and lower extremity stress fractures. Both men and women can benefit from the same preventative measures like adequate stretching, appropriate warm-up and cool-down, sport-specific strengthening and conditioning exercises. Treatment options are also generally applicable to both men and women, such as relative rest, icing, anti-inflammatories, and physical therapy [2]. However, to tailor the most effective training regimen for the female athlete it is important to consider sex-specific susceptibilities to injury. By exploring the biomechanical, neuromuscular and cellular mechanisms of injury risk, it is possible to develop and implement appropriate preventative and treatment options tailored specifically to the female population.

1. Bonaiuti D, Shea B, Iovine R, Negrini S, Robinson V, Kemper HC, Wells G, Tugwell P, Cranney A. Cochrane Review on exercise for preventing and treating osteoporosis in postmenopausal women. Eura Medicophys. 2004;40(3):199-209.

2. Cosca DD, Navazio F. Common problems in endurance athletes. Am Fam Physician. 2007;76(2):237-44.

11. Mudd LM, Fornetti W, Pivarnik JM. Bone mineral density in collegiate female athletes: comparisons among sports. J Athl Train. 2007;42(3):403-8.

16. Reid IR. Relationships among body mass, its components, and bone. Bone. 2002;31(5):547-55.
22. Villareal DT, Fontana L, Weiss EP, Racette SB, Steger-May K, Schechtman KB, Klein S, Holloszy JO. Bone mineral density response to caloric restriction-induced weight loss or exercise-induced weight loss: a randomized controlled trial. Arch Intern Med. 2006;166(22):2502-10.
23. Warden SJ, Creaby MW, Bryant AL, Crossley KM. Stress fracture risk factors in female football players and their clinical implications. Br J Sports Med. 2007 41: i38-i43.

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