title: Influence of the psoas major and thigh muscularity on 100-m times in junior sprinters.
abstract: OBJECTIVE
  This study aimed to investigate how the cross-sectional areas (CSA) of the quadriceps femoris (QF)3, hamstrings (Ham), and psoas major (PM) in junior sprinters are related to mean running velocity (MV100m) calculated from official records of 100-m races.
  
  
  METHODS
  In 44 sprinters (22 boys and 22 girls) aged 14-17 yr, cross-sectional images were taken at the upper thigh and midthigh and midway between the fourth and fifth lumbar vertebrae using magnetic resonance imaging. CSA of the three muscles located in both sides were analyzed. For each muscle, the mean values of the CSA of the right and left sides were calculated and used for regression analyses of the relationships between CSA variables and MV100m.
  
  
  RESULTS
  Stepwise multiple-regression analyses produced prediction equations of MV100m with independent variables of QF CSA at the midthigh and PM-to-QF CSA ratio at the upper thigh for boys (R = 0.38) and PM-to-QF CSA ratio at the midthigh for girls (R = 0.33). In the regression model for boys, QF CSA at the midthigh had a negative regression coefficient.
  
  
  CONCLUSIONS
  For junior sprinters of both genders, the higher development of PM relative to QF, rather than absolute muscle size, is a factor in achieving a better performance in 100-m race performance.
authors.affiliation: Sports Photonics Laboratory, Hamamatsu Photonics K.K., Iwata-City, Japan. hoshi@hq.hpk.co.jp
authors.forename: Yoshihiro
authors.initials: Y
authors.lastname: Hoshikawa
authors.forename: Masataka
authors.initials: M
authors.lastname: Muramatsu
authors.forename: Tomomi
authors.initials: T
authors.lastname: Iida
authors.forename: Akiko
authors.initials: A
authors.lastname: Uchiyama
authors.forename: Yoshiharu
authors.initials: Y
authors.lastname: Nakajima
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Kanehisa
authors.forename: Tetsuo
authors.initials: T
authors.lastname: Fukunaga
mesh_terms: D000054:Acceleration; D000293:Adolescent; D005260:Female; D006801:Humans; D007866:Leg; D008159:Lumbar Vertebrae; D008279:Magnetic Resonance Imaging; D008297:Male; D018482:Muscle, Skeletal / Q000033:anatomy & histology*; D012044:Regression Analysis; D012420:Running / Q000502:physiology*; D012737:Sex Factors; D013848:Thigh