Effect of 7 Months of Physical Training and Military Routine on the Bone Mass of Young Adults.

Introduction: Physical activity (PA) has a great influence on bone mineral density (BMD) and bone mineral content (BMC), however longitudinal studies that seek to relate bone mass to physical activity are scarce and have a small sample size. The aim of this study was to evaluate and compare the effect of 7 months of military physical training (MPT), impact sports (IS), and swimming in the bone mass of young military adults.

Materials And Methods: A prospective study was conducted with 213 military school students (male and aged 19.2 ± 1.2 years) divided into three groups: MPT (n = 144), IS (n = 56), and Swimming (n = 13). Dual-energy X-ray absorptiometry was used to determine body composition (percentage of fat, fat mass, and fat-free mass) and bone mass (BMD, BMD Z-Score, total BMC, arm BMC, leg BMC, and trunk BMC), at the beginning of the military service and after 7 months of training.

Results: It was observed a significant increase in BMD, BMD Z-Score, total BMC and BMC of all segments analyzed for all groups (p < 0.01). There was a significantly greater variation in BMD of the IS group in relation to the MPT group (p < 0.01), and in the arm BMC of the MPT group in relation to the IS group (p < 0.05).

Conclusion: After 7 months of training, there were significant increases in BMC and BMD of all the groups evaluated. The bone response was associated with the muscular group used in the physical exercise and the IS group showed greater gain in BMD.