This study was performed on 19 postmenopausal female volunteers in a period of five months of moderate physical exercise in order to examine beneficial changes in muscle strength and flexibility as well as changes in sex hormone binding globulin (SHBG) and other parameters related to bone metabolism. While SHBG decreased significantly (from 56.0 +/- 20.0 to 43.9 +/- 16.1 nM, P = 0.009) phosphorus and urea increased (from 2.8 +/- 0.4 to 4.0 +/- 0.5 mg/dl, P = 0.00006 and from 32.1 +/- 9.4 to 42.3 +/- 11.0 mg/dl, P = 0.03, respectively). These changes were accompanied by significant increases in muscle strength and flexibility. Other parameters such as alkaline phosphatase and calcium did not change significantly during the study. Plasma levels of SHBG were negatively correlated with phosphorus. As higher SHBG has been related to increased bone loss in older women, we conclude that moderate physical activity is an effective means to preserve bone loss in postmenopausal women.