title: Muscle hypertrophy in prepubescent tennis players: a segmentation MRI study.
abstract: OBJECTIVE
  To asses if tennis at prepubertal age elicits the hypertrophy of dominant arm muscles.
  
  
  METHODS
  The volume of the muscles of both arms was determined using magnetic resonance imaging (MRI) in 7 male prepubertal tennis players (TP) and 7 non-active control subjects (CG) (mean age 11.0 ± 0.8 years, Tanner 1-2).
  
  
  RESULTS
  TP had 13% greater total muscle volume in the dominant than in the contralateral arm. The magnitude of inter-arm asymmetry was greater in TP than in CG (13 vs 3%, P<0.001). The dominant arm of TP was 16% greater than the dominant arm of CG (P<0.01), whilst non-dominant arms had similar total muscle volumes in both groups (P = 0.25), after accounting for height as covariate. In TP, dominant deltoid (11%), forearm supinator (55%) and forearm flexors (21%) and extensors (25%) were hypertrophied compared to the contralateral arm (P<0.05). In CG, the dominant supinator muscle was bigger than its contralateral homonimous (63%, P<0.05).
  
  
  CONCLUSIONS
  Tennis at prepubertal age is associated with marked hypertrophy of the dominant arm, leading to a marked level of asymmetry (+13%), much greater than observed in non-active controls (+3%). Therefore, tennis particpation at prepubertal age is associated with increased muscle volumes in dominant compared to the non-dominant arm, likely due to selectively hypertrophy of the loaded muscles.
authors.affiliation: Department of Physical Education, University of Las Palmas de Gran Canaria, Las Palmas de Gran Canaria, Spain. jsanchis@def.ulpgc.es
authors.forename: Joaquin
authors.initials: J
authors.lastname: Sanchis-Moysi
authors.forename: Fernando
authors.initials: F
authors.lastname: Idoate
authors.forename: Jose A
authors.initials: JA
authors.lastname: Serrano-Sanchez
authors.forename: Cecilia
authors.initials: C
authors.lastname: Dorado
authors.forename: Jose A L
authors.initials: JA
authors.lastname: Calbet
mesh_terms: D015502:Absorptiometry, Photon; D000704:Analysis of Variance; D001132:Arm / Q000503:physiopathology*; D002648:Child; D007839:Functional Laterality / Q000502:physiology*; D006801:Humans; D006984:Hypertrophy / Q000503:physiopathology; D008279:Magnetic Resonance Imaging; D008297:Male; D018482:Muscle, Skeletal / Q000503:physiopathology*; D013030:Spain; D013715:Tennis / Q000502:physiology*