The elderly population is increasing in Spain. The aging process is associated with gradual declines in physical fitness and functional ability. These facts can lead to serious public health problems with the appearance of degenerative diseases and the resulting economic cost for their treatment. There is a lost of strength, a not constant decrease of VO2max and a progressive but not linear decreasing of specific joint mobility with advancing age. In addition, balance disorders are common in elderly people and these alter basic parameters of locomotion. Significant changes occur in body composition with aging: fat free mass decreases and it determines low energy expenditure in basal metabolism and an increasing of fat mass.