Objective: To examine the effect of an eight-week moderate intensity walking program on bone turnover markers, serum osteoprotegerin (OPG) and soluble receptor-activator of nuclear factor- kappa beta ligand (sRANKL) in post-menopausal women. Material and Methods: Twelve post-menopausal women (45-62 years) completed an eight-week walking program at moderate intensity (60-65% maximum heart rate reserve). Non-walking women served as the control group (CG; n= 11). Body weight, percent body fat, body mass index (BMI), estimated maximal oxygen consumption (estimated VO2(max)), bone turnover markers, sRANKL, serum OPG and sRANKL/OPG ratio were measured before and after the intervention. Results: Eight-week walking program produced significant increases in VO2(max) and reductions in body weight and BMI. Serum intact parathyroid hormone (iPTH), and beta- crosslaps (CTx) reduced (p< 0.01, for both), sRANKL/OPG ratio (p< 0.01) and sRANKL values (p< 0.05) increased in the exercise group (EG). We detected significant reductions in the serum OPG levels of EG and CG (p< 0.01). No significant differences were observed between the changes in EG and CG in terms of bone turnover markers, OPG and sRANKL values. Conclusion: Eight-week moderate intensity walking program is beneficial for improving cardiorespiratory function in post-menopausal women to enable them to lead a less risky and a more independent life; however, it seems not so effective in changing the bone turnover markers and the OPG/sRANKL system
