title: Peak-bone-mass development in young adults: effects of study program related levels of occupational and leisure time physical activity and exercise. A prospective 5-year study.
abstract: CONCLUSIONS
  Young adulthood is characterized by profound life-style changes. This study suggests that reduction of sport or exercise, induced by alteration of the occupational situation, negatively impacts generation/maintenance of peak bone mass. In order to compensate occupational-related reductions of physical activity, workplace exercise programs will be helpful.
  
  
  BACKGROUND
  Only few studies have determined the effect of physical activity or physical exercise on bone mineral density (BMD) in the period of late skeletal maturation, i.e. around peak bone mass. The aim of this article was to determine the long-term effect of different levels of physical activity and exercise directly and indirectly derived by occupation during young adulthood.
  
  
  METHODS
  Sixty-one male and female dental students (DES) and 53 male and female sport students (SPS) 21±2 years old were accompanied over the course (4.8±0.5 years) of their study program. BMD at the lumbar spine (LS), hip, and whole body (WB) were determined using dual-energy X-ray absorptiometry.
  
  
  RESULTS
  Parameters of physical activity increased non-significantly in both groups with no relevant differences between the groups. Indices of exercise, however, increased significantly in the SPS group while a significant decrease was assessed for the DES group. Independent of gender, BMD of the SPS increased significantly (p≤0.007) at all skeletal sites (LS, 2.4±3.9%; hip, 1.6±3.5%; WB, 1.8±2.8%) while BMD of the DES remained unchanged at LS (-0.6±4.4%, p=0.432) and WB (0.5±1.9%, p=0.092) but decreased significantly at the hip (-1.9±4.3%, p=0.010). BMD-changes at LS, hip, and WB differ significantly between SPS and DES (p≤0.017). Results remained unchanged after adjusting for baseline BMD-values that differed (p=0.030 to p=0.082) in favor of the SPS group.
  
  
  CONCLUSIONS
  Changes of exercise levels directly or indirectly caused by occupational factors during young adulthood significantly affected generation and/or maintenance of peak bone mass. Compensatory exercise is thus highly relevant for bone health of young adults.
authors.affiliation: Institute of Medical Physics, Friedrich-Alexander University Erlangen-Nuremberg, Henkestrasse 91, 91052, Erlangen, Germany, Wolfgang.Kemmler@imp.uni-erlangen.de.
authors.forename: W
authors.initials: W
authors.lastname: Kemmler
authors.forename: M
authors.initials: M
authors.lastname: Bebenek
authors.forename: S
authors.initials: S
authors.lastname: von Stengel
authors.forename: J
authors.initials: J
authors.lastname: Bauer
mesh_terms: D015502:Absorptiometry, Photon / Q000379:methods; D000293:Adolescent; D000886:Anthropometry / Q000379:methods; D015519:Bone Density / Q000502:physiology*; D001846:Bone Development / Q000502:physiology*; D004032:Diet; D015444:Exercise / Q000502:physiology*; D005260:Female; D005500:Follow-Up Studies; D006621:Hip Joint / Q000502:physiology; D006801:Humans; D008159:Lumbar Vertebrae / Q000502:physiology; D008297:Male; D009043:Motor Activity / Q000502:physiology*; D016272:Occupational Health; D011446:Prospective Studies; D013177:Sports / Q000502:physiology; D013472:Sunlight; D014807:Vitamin D / Q000031:analogs & derivatives / Q000097:blood; D055815:Young Adult
chemical_list: D014807:Vitamin D; C104450:25-hydroxyvitamin D