ORIGINAL ARTICLE

Physiological factors associated with low bone mineral density in female endurance runners

M Burrows¹, A M Nevill², S Bird² and D Simpson³

¹ University of East London, School of Health and Biosciences, Stratford Campus, Romford Road, London E15 4LZ
² University of Wolverhampton, School of Sport, Performing Arts, and Leisure, Gorway Road, Walsall, West Midlands WS1 3BD, UK
³ Department of Nuclear Medicine, Kent and Canterbury Hospital, Canterbury, Kent CT1 3NG, UK

Correspondence to:
Correspondence to:
Dr Burrows, University of East London, School of Health and Biosciences, Stratford Campus, Romford Road, London E15 4LZ, UK;
m.burrows{at}uel.ac.uk

Objective: To explore potential factors that could be associated with low bone mineral density (BMD) in female endurance runners.

Methods: Fifty two female endurance runners (1500 m to marathon), aged 18–44 years, took part. Body fat percentage, lumbar spine BMD, and femoral neck BMD were measured using the Hologic QDR 4500w bone densitometer. Data on training, menstrual cycle status, osteoporosis, and health related factors were obtained by questionnaire. Dietary variables were assessed from a prospective seven day dietary record of macronutrients and micronutrients.

Results: The mean (SD) lumbar spine and femoral neck BMD were 1.11 (0.11) and 0.89 (0.12) g/cm² respectively. A backward elimination regression analysis showed that age, body mass, body fat, distance run, magnesium, and zinc intake were the variables significantly associated with BMD. Lumbar spine BMD (g/cm²) = -1.90 + (0.0486 x age (years)) + (0.342 x log mass (kg)) - (0.000861 x age² (years)) - (0.00128 x distance (km/week)), with an R² = 30.1% (SEE = 0.089 (95% confidence interval (CI) 0.05 to 0.23); p<0.001). Femoral neck BMD (g/cm²) = -2.51 - (0.00989 x age (years)) + (0.720 x log mass (kg)) + (0.000951 x magnesium (mg/day)) -(0.0289 x zinc (mg/day)) - (0.00821 x body fat (%)) - (0.00226 x distance (km/week)), with an R² = 50.2% (SEE = 0.100 (95% CI 0.06 to 0.22); p<0.001). The negative association between skeletal BMD and distance run suggested that participants who ran longer distances had a lower BMD of the lumbar spine and femoral neck. Further, the results indicated a positive association between body mass and BMD, and a negative association between body fat and BMD.

Conclusions: The results suggest a negative association between endurance running distance and lumbar spine and femoral neck BMD, with a positive association between body mass and femoral neck and lumbar spine BMD. However, longitudinal studies are required to assess directly the effect of endurance running and body mass on BMD, and to see if the addition of alternative exercise that would increase lean body mass would have a positive effect on BMD and therefore help to prevent osteoporosis.

Keywords: osteoporosis; endurance running; female athlete triad; diet; lean body mass

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This article has been cited by other articles:

• Bocalini, D. S., Serra, A. J., dos Santos, L., Murad, N., Levy, R. F. (2009). Strength Training Preserves the Bone Mineral Density of Postmenopausal Women Without Hormone Replacement Therapy. J Aging Health 21: 519-527 [Abstract]  
• Barrack, M. T, Rauh, M. J, Barkai, H.-S., Nichols, J. F (2008). Dietary restraint and low bone mass in female adolescent endurance runners. Am. J. Clin. Nutr. 87: 36-43 [Abstract] [Full Text]  

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