Sports Med 2006 36 (7): 561-569 REVIEW ARTICLE 0112-1642/06/0007-0561/$39.95/0 ��� 2006 Adis Data Information BV. All rights reserved. How does Exercise Affect Bone Development during Growth? German Vicente-Rodr�� iguez1,2 1 Department of Physical Education, University of Las Palmas de Gran Canaria, Canary Island, Spain 2 Faculty of Health and Sport Science, University of Zaragoza, Zaragoza, Spain Contents Abstract . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 561 1. Definitions and Context . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 562 2. Biological Maturation, Exercise and Bone Mass . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 563 3. Type and Duration of Sport Participation and Bone Development . . . . . . . . . . . . . . . . . . . . . . . . . . . . 564 4. Soft Tissue Development and Bone Mass . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 565 4.1 Muscle-Bone-Exercise Relationship . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 565 4.2 Fat-Bone-Exercise Relationship . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 566 5. Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 566 It is increasingly accepted that osteoporosis is a paediatric issue. The prepuber- Abstract tal human skeleton is quite sensitive to the mechanical stimulation elicited by physical activity. To achieve the benefits for bone deriving from physical activity, it is not necessary to perform high volumes of exercise, since a notable osteogenic effect may be achieved with just 3 hours of participation in sports. Physical activity or participation in sport should start at prepubertal ages and should be maintained through the pubertal development to obtain the maximal peak bone mass potentially achievable. Starting physical activity prior to the pubertal growth spurt stimulates both bone and skeletal muscle hypertrophy to a greater degree than observed with normal growth in non-physically active children. High strain- eliciting sport like gymnastics, or participation in sports or weight-bearing physi- cal activities like football or handball, are strongly recommended to increase the peak bone mass. Moreover, the increase in lean mass is the most important predictor for bone mineral mass accrual during prepubertal growth throughout the population. Since skeletal muscle is the primary component of lean mass, partici- pation in sport could have not only a direct osteogenic effect, but also an indirect effect by increasing muscle mass and hence the tensions generated on bones during prepubertal years.

562 Vicente-Rodr��iguez Osteoporosis and related fractures are a consider- mass.[20-26] Skeletal muscle development precedes able health concern worldwide.[1] However, the idea bone mass development[27] in such a way that it has that ���senile osteoporosis is a paediatric disease���[2] is been suggested that the increase of muscle strength increasingly accepted.[3-5] In fact, the WHO pro- accompanying muscle development allows for a posed that prevention is the most powerful way to greater generation of forces on bone attachment, fight against the non-communicable diseases, i.e. which stimulate bone growth.[27,28] Although it was osteoporosis.[6] reported that sport participation hardly elicits mus- cle hypertrophy at a prepubertal age,[29] more recent Physical activity, specifically sporting participa- studies have provided evidence of the opposite, i.e. tion during growth, seems to be effective in reducing intensive sport participation is associated with in- the prevalence of osteoporosis-related fractures.[4,7] creased acquisition of muscle mass during However, an increased sedentarism in children[8,9] growth.[30,31] Then, apart from the direct effect of has also been described, which is even more alarm- exercise on bone accrual, exercise could also in- ing in girls because they are usually less active than crease bone acquisition indirectly by increasing boys.[10] For that reason, it is important to know how muscle mass and, hence, the forces generated on the sport activities specifically affect bone develop- bones where the hypertrophied muscles attach. ment, what are the mechanisms involved in the The aim of this article is to summarise current exercise-bone relationship, what is the optimal kind knowledge on the interplay between biological mat- and duration of exercise to stimulate osteogenesis, uration, body composition and exercise on bone and when should the participation in sports start to mass development during growth. maximise the bone mineral peak attained during growth. All this information could help to design 1. Definitions and Context effective, simple, economical and safe physical ac- tivity programmes against osteoporosis and its relat- Many terms are often used when discussing chil- ed social and economic costs.[4] dren and adolescents. ���Growth��� refers to the domi- Sport participation during growth seems to in- nant biological activity for approximately the first crease the peak bone mineral density (BMD) in the 20 years of human life, through changes in size weight-loaded bones of the active subjects by be- underlying three cellular processes: (i) increase in tween 10% and 20% compared with non-physically cell number (hyperplasia) (ii) increase in cell size active counterparts.[11] This effect could be greater (hypertrophy) and (iii) increase in intercellular sub- when exercise starts before the pubertal growth stances (accretion). All these processes occur during spurt.[12-17] In addition, it is clear that at least 25% of growth however, the predominance of one or anoth- the adult total bone mineral content (BMC) is at- er varies with age and the tissue involved. Bone tained in just a 2-year period of fast bone mineral growth is brought about by hyperplasia, hypertrophy accrual during growth (11���13 years in girls and and accretion. 12���14 years in boys).[18] It is also likely that sport These cellular processes are also involved in participation during this period acts synergistically maturation. ���Maturation��� is the progress toward the with the growth-related bone mass accumulation mature stage, referring to the timing and tempo of leading to a higher bone mass at the pubertal peri- the progress. Maturity thus varies with the biologi- od.[18,19] cal system considered. Skeletal maturity is then a The body���s soft tissue components (lean and fat fully ossified adult skeleton. ���Timing��� refers to masses) have been shown to be related to bone when specific maturation event appears, e.g. age at ��� 2006 Adis Data Information BV. All rights reserved. Sports Med 2006 36 (7)