The purpose of the proposed research is to quantify the effect of life style on bone strength and general health parameters by comparing two male populations, one sedentary and the other that has done demanding physical training: (1) Elite infantry recruits who were inducted into the I.D.F. in Feb 1983, did their basic training at Sanur and were part of the 1983 stress fracture project who completed three years of elite infantry service and continued to serve as combat soldiers in the reserves; (2) Yeshiva students who had profiles of 82 or 97 and received deferment from their military service in 1983 and since then have continued their studies and never served in the army.