title: Comparison of the muscle fascicle length between resistance-trained and untrained individuals: cross-sectional observation.
abstract: BACKGROUND
  Muscle plasticity is an important topic in the fields of sport science and physical therapy. The purpose of this study was to examine whether muscle fascicle length increases with resistance training through a comparison between resistance-trained and untrained individuals. If a hypothesis that fascicle length increases by resistance training is true, fascicle length should be longer in the resistance-trained individuals than in the untrained individuals.
  
  
  RESULTS
  Sixteen individuals (age, 21.3 ± 3.3 years; height, 1.74 ± 0.05 m; body mass, 83.6 ± 9.0 kg), who were either body builders or rugby players, were recruited as the training group, and 11 individuals (age, 20.3 ± 2.1 years; height, 1.70 ± 0.06 m; body mass, 54.0 ± 4.7 kg), who did not have regular resistance training experiences, were recruited as the control group. Fascicle length, pennation angle, and muscle thickness of the vastus lateralis and medial gastrocnemius were measured from ultrasonographic images. We found that the muscle thickness and pennation angles in the training group were significantly larger than those in the control group (p < 0.05). However, fascicle length did not significantly differ between the two groups (p > 0.05).
  
  
  CONCLUSIONS
  These results indicate that fascicle length is not associated with muscle size, suggesting that fascicle length would not increase with resistance training.
authors.affiliation: Research Organization of Science and Technology, Ritsumeikan University, 1-1-1 Noji-higashi, Kusatsu, Shiga 525-8577 Japan ; Japan Society for the Promotion of Science, 5-3-1 Kojimachi, Chiyoda-ku, Tokyo, 102-8472 Japan.
authors.forename: Atsuki
authors.initials: A
authors.lastname: Fukutani
authors.affiliation: Faculty of Sport and Health Science, Ritsumeikan University, 1-1-1, Noji-higashi, Kusatsu, Shiga 525-8577 Japan.
authors.forename: Toshiyuki
authors.initials: T
authors.lastname: Kurihara
keywords: Medial gastrocnemius; Muscle thickness; Pennation angle; Ultrasonography; Vastus lateralis