Bone loss over 1 year of training and competition in female cyclists

Abstract

Objective: To observe changes in hip, spine, and tibia bone characteristics in female cyclists over the course of 1 year of training.

Design: Prospective observational study.

Setting: Laboratory.

Participants: Female cyclists (n = 14) aged 26-41 years with at least 1 year of competition history and intent to compete in 10 or more races in the coming year.

Assessment of risk factors: Women who train and compete in road cycling as their primary sport.

Main outcome measures: Total body fat-free and fat mass and lumbar spine and proximal femur areal bone mineral density (aBMD) and bone mineral content (BMC) assessments by dual-energy x-ray absorptiometry. Volumetric BMD and BMC of the tibia were measured by peripheral quantitative computed tomography at sites corresponding to 4%, 38%, 66%, and 96% of tibia length. Time points were baseline and after 12 months of training and competition.

Results: Weight and body composition did not change significantly over 12 months. Total hip aBMD and BMC decreased by -1.4% ± 1.9% and -2.1% ± 2.3% (P < 0.02) and subtrochanter aBMD and BMC decreased by -2.1% ± 2.0% and -3.3% ± 3.7% (P < 0.01). There was a significant decrease in lumbar spine BMC (-1.1% ± 1.9%; P = 0.03). There were no significant bone changes in the tibia (P > 0.11).

Conclusions: Bone loss in female cyclists was site specific and similar in magnitude to losses previously reported in male cyclists. Research is needed to understand the mechanisms for bone loss in cyclists.