title: Association of amount of physical activity with cortical bone size and trabecular volumetric BMD in young adult men: the GOOD study.
abstract: In this population-based study, amount of PA was associated with cortical bone size (increased thickness and periosteal circumference) and trabecular vBMD, but not with cortical vBMD or length of the long bones in young men. The lowest effective amount of PA was > or = 4 h/week.
  
  
  BACKGROUND
  Physical activity (PA) is believed to have positive effects on the skeleton and possibly help in preventing the occurrence of osteoporosis. Neither the lowest effective amount of PA needed to induce an osteogenic response nor its effect on the BMD and size of the different bone compartments (i.e., trabecular and cortical bone) has yet been clarified.
  
  
  METHODS
  In this population-based study, we investigated the amount of all types of PA in relation to areal BMD (aBMD), trabecular and cortical volumetric BMD (vBMD), and cortical bone size in 1068 men (age, 18.9 +/- 0.02 years), included in the Gothenburg Osteoporosis and Obesity Determinants (GOOD) study. aBMD was measured by DXA, whereas cortical and trabecular vBMD and bone size were measured by pQCT.
  
  
  CONCLUSIONS
  The amount of PA was associated with aBMD of the total body, radius, femoral neck, and lumbar spine, as well as with cortical bone size (increased thickness and periosteal circumference) and trabecular vBMD, but not with cortical vBMD or length of the long bones. The lowest effective amount of PA was > or = 4 h/week. aBMD, cortical bone size, and trabecular vBMD were higher in subjects who started their training before age 13 than in subjects who started their training later in life. Our data indicate that > or = 4 h/week of PA is required to increase bone mass in young men and that exercise before and during the pubertal growth is of importance. These findings suggest that PA is imperative for the augmentation of cortical bone size and trabecular vBMD but does not affect the cortical vBMD in young men.
authors.affiliation: Center for Bone Research at the Sahlgrenska Academy, Department of Internal Medicine, Gothenburg University, Gothenburg, Sweden. Mattias.Lorentzon@medic.gu.se
authors.forename: Mattias
authors.initials: M
authors.lastname: Lorentzon
authors.forename: Dan
authors.initials: D
authors.lastname: Mellström
authors.forename: Claes
authors.initials: C
authors.lastname: Ohlsson
mesh_terms: D000293:Adolescent; D000328:Adult; D001835:Body Weight / Q000502:physiology; D015519:Bone Density / Q000502:physiology*; D001842:Bone and Bones / Q000033:anatomy & histology / Q000378:metabolism*; D003430:Cross-Sectional Studies; D015444:Exercise / Q000502:physiology; D005272:Femur Neck / Q000033:anatomy & histology / Q000378:metabolism; D006801:Humans; D008159:Lumbar Vertebrae / Q000033:anatomy & histology / Q000378:metabolism; D008297:Male; D009043:Motor Activity / Q000502:physiology*; D011627:Puberty / Q000502:physiology; D011884:Radius / Q000033:anatomy & histology / Q000502:physiology; D013177:Sports / Q000502:physiology; D013977:Tibia / Q000033:anatomy & histology / Q000502:physiology