title: Maximum toe flexor muscle strength and quantitative analysis of human plantar intrinsic and extrinsic muscles by a magnetic resonance imaging technique.
abstract: BACKGROUND
  The aims of this study were to investigate the relationships between the maximum isometric toe flexor muscle strength (TFS) and cross-sectional area (CSA) of the plantar intrinsic and extrinsic muscles and to identify the major determinant of maximum TFS among CSA of the plantar intrinsic and extrinsic muscles.
  
  
  METHODS
  Twenty six young healthy participants (14 men, 12 women; age, 20.4 ± 1.6 years) volunteered for the study. TFS was measured by a specific designed dynamometer, and CSA of plantar intrinsic and extrinsic muscles were measured using magnetic resonance imaging (MRI). To measure TFS, seated participants optimally gripped the bar with their toes and exerted maximum force on the dynamometer. For each participant, the highest force produced among three trials was used for further analysis. To measure CSA, serial T1-weighted images were acquired.
  
  
  RESULTS
  TFS was significantly correlated with CSA of the plantar intrinsic and extrinsic muscles. Stepwise multiple linear regression analyses identified that the major determinant of TFS was CSA of medial parts of plantar intrinsic muscles (flexor hallucis brevis, flexor digitorum brevis, quadratus plantae, lumbricals and abductor hallucis). There was no significant difference between men and women in TFS/CSA.
  
  
  CONCLUSIONS
  CSA of the plantar intrinsic and extrinsic muscles is one of important factors for determining the maximum TFS in humans.
authors: Department of Sport and Health Science, Ritsumeikan University, 1-1-1 Noji Higashi, Kusatsu, Shiga 525-8577, Japan.
authors: Toshiyuki
authors: T
authors: Kurihara
authors: Future Institute for Sport Sciences, Tokyo, Japan.|Graduate School of Human Health Sciences, Tokyo Metropolitan University, 1-1 Minami-Osawa, Hachioji-shi, Tokyo 192-0397, Japan.|Faculty of Associated Medical Sciences, Khon Kaen University, Khon Kaen, Thailand.
authors: Junichiro
authors: J
authors: Yamauchi
authors: Department of Sport and Health Science, Ritsumeikan University, 1-1-1 Noji Higashi, Kusatsu, Shiga 525-8577, Japan.
authors: Mitsuo
authors: M
authors: Otsuka
authors: Department of Sport and Health Science, Ritsumeikan University, 1-1-1 Noji Higashi, Kusatsu, Shiga 525-8577, Japan.
authors: Nobuaki
authors: N
authors: Tottori
authors: Department of Sport and Health Science, Ritsumeikan University, 1-1-1 Noji Higashi, Kusatsu, Shiga 525-8577, Japan.|Future Institute for Sport Sciences, Tokyo, Japan.
authors: Takeshi
authors: T
authors: Hashimoto
authors: Department of Sport and Health Science, Ritsumeikan University, 1-1-1 Noji Higashi, Kusatsu, Shiga 525-8577, Japan.
authors: Tadao
authors: T
authors: Isaka
keywords: CSA of muscles; Imaging technique; Maximum isometric force; Specific force; Toe grip dynamometer