Non-linear growth trends of toe flexor muscle strength among children, adolescents, and young adults: a cross-sectional study
There are only a few studies on the muscular strength of the foot in children and adolescents; thus, the developmental pattern and normative data of these populations during growth are unclear. We sought to elucidate the developmental pattern of the foot muscle strength among children, adolescents, and young adults compared with that of the hand.
A total of 747 children, adolescents, and young adults participated in this study, and their maximum isometric toe flexor strength (TFS), hand grip strength (HGS), and foot length were measured.
TFS was correlated with HGS (r = 0.785), age (r = 0.659), height (r = 0.757), body mass (r = 0.737), and foot length (r = 0.594). Multiple regression analyses revealed that TFS was correlated with age (β = 0.243 in boys; β = 0.461 in girls), squared value of age (age2; β = − 0.296 in boys; β = − 0.260 in girls), and body mass (β = 0.256 in boys; β = 0.311 in girls) in both sexes, indicating a non-linear relationship between age and TFS development. In a regression model for HGS, age was a significant variable, but not age2. HGS increased linearly from childhood until young adulthood, whereas TFS increased from childhood until adolescence and then levelled off.
Our results demonstrate that TFS has a different developmental pattern compared with HGS.
KeywordsGrowth and development Toe flexor strength Isometric contraction
Squared value of age
Squared value of body mass
Squared value of height
Hand grip strength
Peak height velocity
Relative hand grip strength
Relative toe flexor strength
Toe flexor strength
We thank all children and teachers who cooperated with us for this study. The present study was partly supported by a Grant-in-Aid for Scientific Research (C; #22500619) for H. S.; for Young Scientists (B; #24700631 and # 23700688) for M.O., T.K, respectively; for Young Scientists (A; #23680066) for J.Y.; for Exploratory Research (#24650408) for J.Y. from the Ministry of Education, Culture, Sports, Science and Technology of Japan.
All of authors satisfied the following area of authorship requirements: NM: manuscript writing, concept and study design, data acquisition, data analysis, and interpretation. JY: manuscript writing, concept and study design, data acquisition, data analysis, and interpretation. RF: concept and study design, data acquisition, data analysis, and interpretation. TK: concept and study design, data acquisition, data analysis, and interpretation. MO: concept and study design, data acquisition, data analysis, and interpretation. TO: concept and study design, data acquisition, data analysis, and interpretation. NS: concept and study design, data acquisition, data analysis, and interpretation. IK: concept and study design, data acquisition, data analysis, and interpretation. HS: concept and study design, data acquisition, and significant manuscript reviewer/reviser.
Compliance with ethical standards
Conflict of interest
The authors declare that they have no competing interest.
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