title: Exercise characteristics influence femoral cross-sectional geometry: a magnetic resonance imaging study in elite female athletes.
abstract: The associations between mid-femoral cross-sectional geometry and exercise characteristics were investigated in female athletes. The effects on bone geometry for weight-bearing sports with low-to-high-impact were greater than those for non-impact weight-bearing sports, whereas low-impact or high-strain-magnitude/low-strain-rate sports had less of an effect on bone geometry compared with higher-impact sports.
  
  
  BACKGROUND
  Many previous studies have investigated tibial geometry in athletes; however, few studies have examined the associations between femoral cross-sectional geometry and exercise characteristics. The aim of this study was to investigate these relationships using magnetic resonance imaging (MRI) at the femoral mid-shaft.
  
  
  METHODS
  One hundred and fifty-three female elite athletes, aged 18-34 years, were classified into five groups based on the characteristics of their sports. Sports were considered non-impact (n = 27), low- or moderate-impact (n = 39), odd-impact (n = 38), high-strain-magnitude/low-strain-rate (n = 10), or high-impact (n = 39). Bone geometrical parameters, including cortical area, periosteal perimeter, and moment of inertia (bone strength index), were determined using MRI images.
  
  
  RESULTS
  Higher-impact groups displayed bone expansion, with significantly greater periosteal perimeters, cortical areas (~37.3%), and minimum moments of inertia (I(min,) ~92.3%) at the mid-femur than non- and low-impact groups. After adjusting for age, height, and weight, the cortical area and I(min) of the low-impact and high-strain-magnitude/low-strain-rate groups were also significantly greater than those of the non-impact group.
  
  
  CONCLUSIONS
  Higher-impact sports with high strain rates stimulated periosteal bone formation and improved bone geometry and strength indices at the femoral mid-shaft. Although our results indicate that weight-bearing sports are beneficial even if they are low impact, the effects of lower-impact or high-strain-magnitude/low-strain-rate sports on bone geometry were less pronounced than the effects of higher-impact sports at the femoral mid-shaft.
authors.affiliation: Laboratory for Exercise Physiology and Biomechanics, School of Health and Sport Sciences, Chukyo University, 101 Tokodachi, Kaizu-cho, Toyota, 470-0393, Aichi, Japan, a.hond0920@gmail.com.
authors.forename: A
authors.initials: A
authors.lastname: Honda
authors.forename: M
authors.initials: M
authors.lastname: Matsumoto
authors.forename: T
authors.initials: T
authors.lastname: Kato
authors.forename: Y
authors.initials: Y
authors.lastname: Umemura
mesh_terms: D000293:Adolescent; D000328:Adult; D056352:Athletes; D015444:Exercise; D005260:Female; D005269:Femur / Q000033:anatomy & histology / Q000502:physiology; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods; D013177:Sports; D016474:Weight-Bearing; D055815:Young Adult