Question: 

Through the regulation of the osteocalcin (OC)/ undercarboxylated osteocalcin (ucOC) balance, bone regulates energy metabolism. Cycling is a not-weight-bearing activity with a strong impact on energy metabolism and known to induce bone resorption. We evaluated the relationship between OC and ucOC and the energy status markers in elite cyclists during a stage race.

Methodology: 

9 cyclists engaged in 2011 Giro d'Italia were recruited. Pre-analytical and analytical phases tightly followed the international recommendations. Blood drawings were performed at days -1, 12 and 22. Plasma/serum were assayed by ELISA for total-OC, ucOC, adiponectin, leptin. Concentrations were corrected for plasma volume changes occurring during the race. Anthropometrical data and energy consumption were recorded. Data were compared over time by ANOVA and markers trend was correlated by Pearson's test.

Results: 

The energy expenditure increased over the race (p<0.001). Total-OC decreased (p<0.01) over the race, ucOC did not change; however the ratio ucOC/OC increased significantly (p<0.01). Despite no changes in Fat mass %, leptin decreased (p<0.01) and adiponectin increased (p<0.001). Body mass and BMI both decreased (p<0.01). ucOC/OC positively correlated with adiponectin (p<0.01, r=0.49) and negatively with leptin (p<0.01, r= –0.46) and BMI (p<0.05, r= –0.41).

Conclusions: 

3-weeks cycling stage race induced a decrease in total-OC and a shift towards a relative increase of ucOC. A relationship between bone derived OC isoforms and adipose hormones was evident with a link of sequentiality: ucOC/OC increase was stronger in the first half, changes in leptin and adiponectin were stronger in the second half of the race.