Reducing Stress Fracture in Physically Active Military Women (1998) / Chapter Skim
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2 Bone Health and Risk Factors
2 Bone Health and Risk Factors
Pages 29-42
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From page 29... ...
Bone mass, which may continue to accumulate upto age 30, may be adversely affected by inadequate calcium intakes during adolescence and early adulthood. Achievement of an insufficient peak bone mass is considered one of the major risk factors for subsequent development of osteoporosis (Lu et al., 1994; Recker et al., 1992; Teegarden et al., 19951.
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From page 30... ...
BONE MINERAL DENSITY Peak bone mass is most often measured and referred to as bone mineral density (BMD, g/cm2~i because of the strong correlation between BMD and bone strength (Bouxsein and Marcus, 1994; Moro et al., 1995~. Many studies have found associations between low BMD and history of previous fracture (Gluer et al., 1996; Honkanen et al., 1991~.
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From page 31... ...
Fitness level at baseline, smoking history, and BUA were independent predictors of stress fracture risk, and those soldiers who developed fractures were found to have a greater decrease in BUA earlier In basic trading than did soldiers who did not develop fractures. This decline in BUA during basic trading indicates Mat soldiers respond to the additional bone stresses during this period with increased bone turnover, which causes transiently downward adjustment in bone strength due to an expansion of the remodeling space (Kimmel, 19971.
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From page 32... ...
Bone Mass Of the wide variety of techniques available to measure bone mass, DXA is the most frequently used method, measuring total body as well as specific regions of bone. Since DXA involves measurement In only two dimensions, it does not provide a true estimate of density, the three-dimensional measurement (Beck et al., 19971.
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From page 33... ...
No consistent association has been found between the occurrence of stress fracture and calcium intake in either athletes or military recruits, possibly due to the relatively high calcium intakes in both groups (Bennell et al., 1996; Schwellnus and Jordaan, 1992)
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From page 35... ...
Forces generated by skeletal muscles appear to extend beyond generalized bone mineral effects; actual bone morphology and geometry are, to some extent, shaped by forces generated by skeletal muscles. Finally, as art example of Me strong skeletal muscl~bone mineral association, quadriceps and hamstring skeletal muscle sledge Independently predict humerus and spine bone mineral density after controlling for such other relevant factors as 4 "[A]
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From page 36... ...
Thus, fat mass and skeletal muscle mass, two body composition components extrinsic to the skeleton, appear to have important influences on the growth, mass, shape, geometry, and strength of bone. Physical activities that generate a large muscle force can cause stress fractures at selected anatomic locations.
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From page 37... ...
However, unlike a low level of aerobic fitness in which the person is simply unable to complete a physical task at a higher intensity until metabolic and cardiorespiratory adaptations are sufficient, even sedentary people can tolerate a large volume of cyclic loading to their skeletal system for a period of several weeks before symptoms of stress fracture occur. The architectural adaptations to bone that permit cyclic loading at higher levels of physical activity are not required in the first few weeks of training, and any excessive strain produced during this early phase does not impair a person's ability to participate until such time as the cumulative stress produces clinically obvious symptoms.
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From page 38... ...
can assist in reducing the number of Tower limb injuries arising from sport and training activities. However, it has been reported that a training shoe is rarely implicated in a stress fracture injury (Nike, 1987~.
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From page 39... ...
Exogenous estrogen-progestagen hormones given to women of reproductive status may positively affect peak bone mass reached in adulthood and the rate of premenopausal bone loss, both of which are important for fixture fracture risks. In contrast, long-acting progestagens used alone may have a detrimental effect on BMD.
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From page 40... ...
, a survey was conducted in 1,000 premenopausal military women to assess dietary calcium intakes, physical activity, and habits affecting skeletal health. In a subset of 90 women who completed bone density testing by DXA, the attainment of peak bone mass was unaffected by history of smoking, alcohol, and caffeine use during high school.
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From page 41... ...
While skeletal muscles insulate bone and absorb mechanical loading, excessive muscular development can generate large muscle force and may cause stress fractures at selected anatomic locations. Regular participation in physical activity develops muscular strength, skill and readiness.
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