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ACSM Special Content

Scanning Sports Medicine

Jaworski, Carrie A. MD, FACSM

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Current Sports Medicine Reports: October 2007 - Volume 6 - Issue 5 - p 278
doi: 10.1097/01.CSMR.0000306486.30777.66
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The following is a preview of select articles that published in Medicine & Science in Sports & Exercise 2007, Volume 39, Number 9.

The Effect of Oral Contraceptives on Bone Mass and Stress Fractures in Female Runners

This randomized trial attempted to determine the effect of oral contraceptives (OCs) on bone mass and stress fracture incidence in young female distance runners. A total of 150 competitive female runners aged 18 to 26 years were assigned to OCs or no intervention for 2 years. Bone mineral density (BMD) and content (BMC) were measured yearly using dual x-ray absorbitometry while stress fractures were confirmed by imaging. Randomization to OCs was unrelated to changes in BMD or BMC in oligo-amenorrheic or eumenorrheic runners. Treatment-received analysis, which analyzed for actual OC use, showed that oligo-amenorrheic runners who used OCs gained about 1% per year in spine BMD (P < 0.005) and whole-body BMC (P < 0.005). This amount is similar to those who regained periods spontaneously and was significantly greater than those who remained oligo-amenorrheic. Randomization to OCs did not demonstrate a significant reduction in stress fracture incidence, but the direction of the effect was protective in all groups, with a stronger effect seen in the treatment-received analysis. The main limitation of this study was a higher than anticipated rate of noncompliance. Bottom line: The data suggest that OC use is not detrimental to BMD or BMC in female runners and may protect against stress fractures. Definitive proof of the effect that hormonal therapy has on BMD or BMC will be difficult to demonstrate in this group.

Risk Factors for Stress Fractures Among Young Female Cross Country Runners

The authors of the above study also used the information they collected to conduct a prospective study of risk factors for stress fracture among 127 competitive female distance runners. Eighteen self-reported stress fractures occurred during this study, which were then confirmed through imaging studies. Using multivariate analysis, baseline characteristics associated with an increased risk of stress fracture were found to include one or more previous stress fractures, lower whole-body bone mineral content, younger chronological age, lower dietary calcium intake, and younger age at menarche. History of menstrual irregularity was also associated with an increased risk, but not at a statistically significant level. Training-related factors did not affect risk in this study. Bottom line: While this study is small in number and limited to distance runners, it offers prospective data on modifiable risk factors that need to be monitored and addressed in all young female athletes in order to decrease risk of stress fracture.

Exercise and Calcium Supplementation: Effects on Calcium Homeostasis in Sportswomen

The aim of this study was to quantify the increase in 24-hour total dermal calcium losses and the net changes in calcium retention in active women following strenuous exercise for 1 hour. A secondary goal was to determine the role of calcium supplementation on calcium homeostasis in physically active women. The hypothesis was that supplementation would correct exercise-induced calcium losses. Twenty-six active premenopausal women completed three 8-day intervention phases in a randomized order, cross-over design. The three phases were placebo + no exercise, placebo + exercise, and 400-mg calcium carbonate twice daily + exercise. Diet was provided with a standard calcium amount (450 mg/day); 24-hour pooled urine and fecal collections allowed determination of calcium balance; and a 24-hour dermal collection was made at the end of each phase. Results demonstrated significantly increased dermal calcium losses with exercise, which was no longer significant when calcium supplementation was provided. Net calcium retention was only positive during the exercise + calcium intervention. Bottom line: Calcium supplementation can correct for negative calcium balance from low dietary intake and dermal losses from exercise.

© 2007 American College of Sports Medicine