Physical activity and osteoporosis

Osteoporosis is one of the most prevalent muscle-skeletal problem around the world, affecting persons even in the developing countries. Although women are more sensitive (about 30% of elderly American women), there is an increasing prevalence in men (4 to 6% among men over 50), in this case mostly as consequence of metabolic bone disfunction because alcohol, drugs and other deseases. Osteoporosis is characterized by low bone mass and microarchitetural deterioration of bone tissue, leading to enhanced bone fragility and a consequent increase in fracture risk. Bone mineral density (BMD) is the most popular assessment method, and accounts for 75-85% of variance in ultimate strength of bone tissue. It is consider normal when no lower than 1 SD bellow the mean for young adult women; osteopenic if between 1.0 and 2.5 SD bellow the mean; and osteoporosis if BMD 2.5 SD bellow or more (WHO, 1994). Fracture is among the worst consequences, and its risk increased 1.5- to 3-fold for each SD fall in BMD (Marshall, 1996), and even worse for hip fracture: 2.4- to 3-fold for each 1 SD decline in BMD (Cummins, 93). Preventive measures should be adress to factors involved in the bone mass accumulation during youth (peak bone mass) and to the subsquent rate of bone loss. A compreensive recent review (Vuori, 2001) reported that numerous cross sectional studies in athletes, populational samples, some longitudinal studies, at least seven RCTs and several control trials show evidence (Category A) that physical activity in youth can contribute to increase peak bone mass. Moreover, quantitative analyses show strong evidence (Category A) that PA can be effective in mantaing bone mass in premenopausal women, and decreasing substantially loss of bone in postmenopausal women. In general, that effect was about 1%-yr-1 among exercisers, as consequence of inhibited osteoclastic resorption at external anatomical growth modelling sites. Addition occurs both by layering on existing cancellous surfaces and by creation of new immature scaffold, with the novo incorporation of a rich, capillary blood vessel supply (Boyde, 2003). Recently, it was showed that accumulated exercise has an impact even better than continuous on BMD and bone cross-sectional area (Robling, 2002). Considering aging population will be increasing dramatically, particularly in the developing world where access to any facility is difficult, it is important to take initiatives in training muscle strength and balance that may be feasible to those regions. The use of home exercise, taking adapted devices in strength exercise seems to be promising in reaching a public health approach instead a clinical one. In those lines, positive results (Vilamarin 2000; Raso 2001; Matsudo S, 2004); observed in our research center will be presented. The role of sedentariness, ethnics, low and high impact training, sexual maturation, nutrition, hormones, NO2, overtraining, hydrogymnastic, and sport/exercise protocol will be discussed.