title: Relationship between lateral differences in the cross-sectional area of the psoas muscle and curve running time.
abstract: BACKGROUND
  The aim of this study was to investigate whether lateral differences in the cross-sectional areas of the hip and thigh muscles were related to curve sprinting time.
  
  
  METHODS
  Thirteen college students (10 men and 3 women; mean ± SD: age, 20.4 ± 1.7 years; height, 167.6 ± 8.9 cm; mass, 57.4 ± 5.4 kg) participated in this study. The participants were instructed to sprint along a circular track (23 m radius) in the counterclockwise and clockwise directions. Magnetic resonance imaging was used to measure the cross-sectional area of the psoas major, quadriceps femoris, and hamstring muscles. The symmetry index was used to evaluate the lateral differences in the cross-sectional area.
  
  
  RESULTS
  The lateral difference was observed in the cross-sectional area (CSA) of the thigh muscles, not in the psoas major muscle. The sprint time was not significantly different between the counterclockwise (22.15 ± 2.27 s) and clockwise (22.13 ± 2.32 s) directions. No significant correlations were found between the symmetry index of the thigh muscles and the cross-directional differences in sprint time. However, the symmetry index of the psoas major muscle correlated significantly with the cross-directional difference in sprint time (r = -0.614, P = 0.026).
  
  
  CONCLUSIONS
  These findings suggest that the participants in whom the cross-sectional area of the psoas major muscle of the outer leg was larger than that of the inner leg were faster in curve sprinting.
authors.affiliation: Department of Sport and Health Science, Ritsumeikan University, Kusatsu, Shiga, Japan.
authors.forename: Nobuaki
authors.initials: N
authors.lastname: Tottori
authors.affiliation: Department of Sport and Health Science, Ritsumeikan University, Kusatsu, Shiga, Japan. t-kuri-a@st.ritsumei.ac.jp.
authors.forename: Toshiyuki
authors.initials: T
authors.lastname: Kurihara
authors.affiliation: Department of Sport and Health Science, Ritsumeikan University, Kusatsu, Shiga, Japan.
authors.forename: Mitsuo
authors.initials: M
authors.lastname: Otsuka
authors.affiliation: Department of Sport and Health Science, Ritsumeikan University, Kusatsu, Shiga, Japan.
authors.forename: Tadao
authors.initials: T
authors.lastname: Isaka
mesh_terms: D000328:Adult; D019412:Anatomy, Cross-Sectional; D000885:Anthropology, Physical; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D016658:Psoas Muscles / Q000502:physiology*; D012420:Running / Q000502:physiology*; D013848:Thigh / Q000502:physiology; D055815:Young Adult
references.citation: J Physiol Anthropol. 2011;30(2):47-53
references.pmid: 21483176
references.citation: J Biomech Eng. 1985 May;107(2):96-103
references.pmid: 3999718
references.citation: J Exp Biol. 2007 Mar;210(Pt 6):971-82
references.pmid: 17337710
references.citation: J Strength Cond Res. 2010 Jun;24(6):1472-9
references.pmid: 20508447
references.citation: Scand J Med Sci Sports. 2016 Oct;26(10 ):1171-9
references.pmid: 26408499
references.citation: J Strength Cond Res. 2005 Aug;19(3):615-21
references.pmid: 16095411
references.citation: Clin Biomech (Bristol, Avon). 1992 May;7(2):109-19
references.pmid: 23915688
references.citation: J Exp Biol. 2012 Jun 1;215(Pt 11):1944-56
references.pmid: 22573774
references.citation: PLoS One. 2011;6(7):e22858
references.pmid: 21829539
references.citation: Res Q Exerc Sport. 1980 May;51(2):432-6
references.pmid: 7188591
references.citation: Biol Lett. 2006 Mar 22;2(1):47-50
references.pmid: 17148323
references.citation: J Sports Sci. 2015;33(6):552-60
references.pmid: 25495196
references.citation: J Appl Physiol (1985). 2000 Nov;89(5):1991-9
references.pmid: 11053354
references.citation: J Physiol Anthropol. 2010;29(1):13-21
references.pmid: 20453429
references.citation: Gait Posture. 2006 Jan;23(1):106-11
references.pmid: 16311202
references.citation: Med Sci Sports Exerc. 2011 Jul;43(7):1260-71
references.pmid: 21131859
references.citation: Med Sci Sports Exerc. 2006 Dec;38(12):2138-43
references.pmid: 17146321
references.citation: Neuropsychologia. 1987;25(3):579-84
references.pmid: 3683814
references.citation: Res Q Exerc Sport. 2012 Jun;83(2):160-7
references.pmid: 22808701
references.citation: Sports Biomech. 2015 Mar;14(1):106-21
references.pmid: 25896099
references.citation: J Sports Sci. 2009 Jan 15;27(2):129-38
references.pmid: 19031332