 Bone loss by ageing is partly compensated by increased bone size, partly preserving bone strength. This is of relevance as a Strength Index, taking both bone size and bone mass into account, probably predict future fractures better than bone mass. Two years daily school gymnastics enhanced bone mass and bone size, reduce the fatness and cardiovascular risk factors for disease. Exercise increase bone mass also after puberty but the benefit is lost with cessation of exercise. In spite of this have elderly former active individuals less fractures than inactive people. 