Bone mass develops throughout childhood and adolescence until a peak bone mass is achieved during early adulthood. Fracture risk later in life can be predicted at a large extent by peak bone mass. Occurence of sarcopenia and osteoporosis (i.e. loss of mone mass) during late adulthood has been strongly associated with the degree of bone mineralization during early life. Nearly 50% of total bone mineral content (BMC) reached during adulthood is obtained during pre-adolescence rendering this period critical for skeletal health and is considered as an optimal period for bone/skeletal growth since during this time bones are more adaptable to osteogenic stimuli such as exercise-induced mechanical loading. Organized sport activities and/or nutrition appear to affect profoundly bone mineral density (BMD), BMC, bone geometry, and overall skeletal health during preadolescence offering an effective type of prevention of osteoporosis, a condition very difficult to treat later in life. Evidence suggest that some modes of exercise activities may be more effective (osteogenic) for bone development due to the magnitude and type of mechanical strain placed on long bones causing them to be more dense. Weight-bearing activities (e.g. running, jumping etc.) are believed to be more osteogenic than non-weight bearing activities. However, more research is required in order to determine: i) whether weight-bearing activities are more osteogenic than non weight -bearing activities during childhood and ii) the osteogenic potential of a large number of sport activities used by school-children as compared to a control treatment of no participation in organized sport activities. The present trial attempted to compare a large number of different sport activities in respect to their osteogenic potential based on training variables that are thought to affect osteogenesis while at the same time allows direct comparison of exercise modes that are entirely different. Therefore, the goal of this investigation was to determine the osteogenic potential of a large number of exercise training activities in boys and girls of 8-12 years of age during an entire primary school season.