Bone strength and peak bone mass are preliminary determined by genetic factors. Life style, especially exercise, is also considered to have an important effect on bone strength. Bone has the ability to strengthen itself according to Wolff's Law. When bone is subjected to strains and/or strain rates higher than the usual, it responds by remodeling, strengthening its architecture. The ability is greatest in young individuals and decreases with age. In the elderly this ability is largely non-existent and bone mass is lost. Whether this loss leads to osteoporosis is largely a function of the peak bone mass achieved before the decline. 11% of males and 44 % of females over 50 suffer from osteoporosis in later life. To what extent vigorous exercising beginning at a young age can increase bone strength is not known.