After a run-in period of supplementation of vitamin D for two months, participants will be randomized into three different equally sized groups (n=25): Group A will receive power training. Group B will have progressive strength training. Group C will serve as a control group. They will receive a consultation about leading a healthy life with special attention being paid to nutrition and physical activity. The intervention period lasts for 12 weeks. The 60 minutes training sessions will be held two times a week by members of the Institute of Sport Science and Sports of the University of Erlangen-Nuremberg. Follow-up visits are scheduled three and six months after intervention period.