Osteocartilaginous metabolic markers change over a 3-week stage race in pro-cyclists

Abstract

Evidence suggests that endurance and even recreational cycling may stimulate bone resorption; however, little is known about cartilage response to endurance cycling exercise. We investigated effort-dependent changes in bone turnover and cartilage biomarkers in blood and urine samples from elite cyclists during a 3-week stage race. Whole blood and urine samples were collected the day before the start of the race, at mid and end-race for serum and urinary CTx-I, NTx-I, PINP, COMP (only in serum), and CTx-II analysis by enzyme-linked immunosorbent assay. The values were corrected for plasma volume or creatinine excretion, respectively, and correlated with power output (corrected for body weight) and net energy expenditure. Bone marker concentrations in both serum and urine were slightly but significantly decreased. Among the cartilage degradation markers, only CTx-II was decreased, while COMP remained unchanged. The changes in bone and cartilage turnover indexes were correlated with the indexes of physical effort and energy consumption.

Strenuous physical effort, in the absence of mechanical loading, slows bone metabolism and only minimally affects cartilage turnover. Since changes in plasma and urine volume, which normally occur in exercising athletes, can mask these effects, biomarker concentrations need to be corrected for shifts in plasma volume and urinary creatinine for correct interpretation of the data.

Key Words::

• Physical endurance
• bone remodeling
• cartilage
• mechanical stress
• energy expenditure

Acknowledgements

The authors are indebted to the Liquigas Pro-cycling team for their logistic support and availability. The authors are grateful to Mr Kenneth Britsch for language editing.

Declaration of interest: The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.

This study was funded by the Italian Ministry of Health. The funding source had no role in the study.

Supplementary material available online

Supplementary Table I, available online at http://informahealthcare.com/doi/abs/10.3109/00365513.2015.1057762.