Abstract
Data supporting physical activity guidelines to optimize bone development in men is sparse. Peak bone mass is believed to be important for the risk of osteoporosis later in life. The objective of this study was to determine if an increased amount of physical activity over a 5-year period was associated with increased bone mineral content (BMC), areal (aBMD) and volumetric (vBMD) bone mineral density, and a favorable development of cortical bone size in young adult men. The original 1068 young men, initially enrolled in the Gothenburg Osteoporosis and Obesity Determinants (GOOD) study, were invited to participate in the longitudinal study, and a total of 833 men (78%), 24.1 ± 0.6 years of age, were included in the 5-year follow-up. A standardized self-administered questionnaire was used to collect information about patterns of physical activity at both the baseline and 5-year follow-up visits. BMC and aBMD were measured using dual energy X-ray absorptiometry, whereas vBMD and bone geometry were measured by peripheral quantitative computed tomography. Increased physical activity between the baseline and follow-up visits was associated with a favorable development in BMC of the total body, and aBMD of the lumbar spine and total hip (p < 0.001), as well as with development of a larger cortex (cortical cross sectional area), and a denser trabecular bone of the tibia (p < 0.001). In conclusion, increased physical activity was related to an advantageous development of aBMD, trabecular vBMD and cortical bone size, indicating that exercise is important in optimizing peak bone mass in young men. © 2012 American Society for Bone and Mineral Research.
Highlights
In a cross-sectional analysis in the Gothenburg Osteoporosis and Obesity Determinants (GOOD) study, that physical activity was associated with areal bone mineral density (aBMD) and cortical bone size in 18- to 20-year-old Swedish men, and that the boys who began their physical activity before puberty had higher adult aBMD and cortical bone size than boys who started training later.[16]
For each hour of increased physical activity, aBMD of the lumbar spine and bone mineral content (BMC) of the total body increased by 0.005 g/cm2 and 5.4 g, respectively, while cortical CSA and total CSA of the tibia increased by 0.36 mm2 and 0.49 mm2, respectively, between the baseline and follow-up visits (Table 1)
Our data indicate that the physical activity accompanied increase in aBMD was due to increased cortical bone size and trabecular volumetric BMD (vBMD). Both cortical bone size and bone mineral density (BMD) are important determinants of bone strength and resistance against fracture.[24,25] As the resistance of bone to bending and torsion forces is related exponentially to its diameter, even a small difference in the outer circumference could make a substantial contribution to its strength and resistance to fracture.[24]. In the present study, we found that increased physical activity was related to augmented cortical bone size via actions on the outer cortical envelope, indicating attained benefits of physical activity in enlarging the cortical shell, even though physical activity was increased after entering adulthood
Summary
A few small longitudinal studies[12,13] have found that a maintained high level of physical activity was associated with preserved areal bone mineral density (aBMD) in both young adult men[12] and women.[13,14] neither of these studies were able, due to limited statistical power, to investigate whether changed physical activity was related to altered aBMD. There are no population-based longitudinal studies that have investigated the association between increased level of physical activity and bone development in young adult men. In the large majority of previous studies investigating the association between exercise and bone mass, bone properties have been measured using dual energy X-ray absorptiometry (DXA). Because the DXA technique cannot distinguish whether changes in aBMD are due to bone volumetric BMD or in bone geometrical parameters,(15) data regarding the role of physical activity on bone structural parameters is scarce.
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