Osteoporosis is defined as a systemic skeletal disease characterized by low mineral bone mass and microarchitectural deterioration of bone tissue1, 2, 3. More specifically, it involves a decrease in the number of trabeculae coupled with trabecular thinning and loss of connectivity and a reduction in cortical thickness and an increase in its porosity1, 2, 3. This consequently increases bone fragility and susceptibility to fracture2, 3, 4, 5. Worldwide, osteoporosis causes more than 8.9 million fractures yearly, resulting in an osteoporotic fracture occurring about every 3 seconds6, 7, 8. Using the WHO definition of osteoporosis, osteoporosis affects approximately 6.3% of men over the age of 50 and 21.2% of women over the same age range globally3,6, 7, 8. Based on the world population of men and women, this suggests that approximately 500 million men and women worldwide may be affected6, 7, 8. 80%, 75%, 70%, and 58% of forearm, humerus, hip and spine fractures, respectively, occur in women3,6, 7, 8. Overall, 61% of osteoporosis fractures occur in women, with a female-to-male ratio of 1.63,6, 7, 8.

Peak bone mass is considered the single most important factor for the prevention of osteoporosis later in life9. In fact, an increase in peak bone mass of 10% would delay the onset of osteoporosis by 13 years10. In comparison, it has been reported that a 10% increase in the age of menopause, or a 10% reduction in age-related (non-menopausal) bone loss would only delay the onset of osteoporosis by 2 years10. In addition, based on epidemiological studies, a 10% increase in peak bone mass could reduce the risk of osteoporotic fractures by 50% in postmenopausal women9, 10, 11.

Peak bone mass has several determinants such as genetics, hormones, nutritional factors and mechanical factors including body weight and weight-bearing physical activity12, 13, 14, 15, 16, 17, 18, 19. An abundance of evidence from interventional studies supports the effectiveness of exercise training on bone mass accrual especially during the growing years (e.g., in children and adolescents). However, only two systematic reviews have consolidated this evidence20,21.

The first systematic review exclusively examined randomized controlled trials that investigated the impact of exercise training on bone strength20. The second review broadened the scope of the aforementioned study by incorporating exercise training effects encompassing interventional and observational studies among children or adolescents21. In this respect, aerobic, resistance, and other types of physical training have been used to explore the osteogenic response in children and adolescents . Diverse results have been obtained22, 23, 24 and no comparison between the osteogenic effects of the different types of physical exercise trainings has been made.

A cross sectional study investigated the relation between maturity and bone mineral density (BMD) in 91 female racquet sport players aged 7-17 and healthy, maturity matched counterparts. Proximal humerus, humeral shaft, and distal radius side to side areal BMD differences were significantly greater in players than controls at Tanner stages 3, 4, and 525. In fact, during this period of puberty, bone is particularly responsive to weight-bearing, high impact exercises25. Gender may affect the osteogenic response to exercise during puberty26,27. Weight-bearing bones seem to be more sensitive to physical exercise in boys than in girls during pre- and early puberty26. Kriemler at al.26 concluded that sex differences in bone mineral content (BMC) during pre- and early puberty may be related to a different sensitivity of bone to physical loading, irrespective of muscle mass. Hence, studying how physical activity affects bone health in young females and whether exercise type influences the extent of its impact on bone mass is crucial. The main aim of this systematic review was to assess the impact of exercise training on bone health parameters in adolescent girls, and the second aim was to investigate whether the type of exercise training can modulate this effect.