Bone Metabolism in Premenopausal Exercising Women

The main goal of this study is to examine how sex hormones and low energy availability affect the concentrations of bone remodelling markers at rest and after a running protocol. The research questions to be addressed are: 1: Does the ovarian hormone profile influence serum bone marker concentrations in women exercising resting and in response to to exercise? 2\. Are there differences in response to low energy availability in bone marker concentrations between eumenorrhoeic female athletes and oral contraceptive users? 3: Is the response of bone markers affected by different exercise stimuli: endurance or aerobic endurance? 4: Do bone markers return to baseline levels after 24 hours of high energy availability diet after 6 days of low energy availability?