title: Fiber type composition of the human quadratus plantae muscle: a comparison of the lateral and medial heads.
abstract: BACKGROUND
  The human quadratus plantae muscle has been attributed a variety of functions, however no consensus has been reached on its significance to foot functioning. The architecture of the human quadratus plantae consists of an evolutionarily conserved lateral head, and a medial head thought to be unique to Man. Surveys of human anatomy have demonstrated the absence of either the medial or lateral head in 20% of the population, which may have implications for foot functioning if each muscle head performs a discrete function.
  
  
  METHODS
  We investigated the quadratus plantae from eleven formalin-embalmed specimens with a mean age of 84 ± 9 years. Immunohistochemical methods were used to determine the percentage of Type I and Type II muscle fibers in the medial and lateral heads of the quadratus plantae from these specimens.
  
  
  RESULTS
  Results showed striking homogeneity in fiber type composition within an individual, with an average difference in Type I fiber content of 4.1% between lateral and medial heads. Between individuals, however, the ratio of fiber types within the quadratus plantae was highly variable, with Type I fiber percentages ranging from 19.1% to 91.6% in the lateral head, and 20.4% to 97.0% within the medial head.
  
  
  CONCLUSIONS
  Our finding of similar fiber type composition of lateral and medial heads within an individual supports the hypothesis that the two heads have a singular function.
authors.affiliation: Current Address: Department of Anatomy and Cell Biology, University of Saskatchewan, 107 Wiggins Rd., Saskatoon, Saskatchewan S7N 5E5 Canada.
authors.forename: Kristen L
authors.initials: KL
authors.lastname: Schroeder
authors.affiliation: Current Address: Department of Anatomy and Cell Biology, University of Saskatchewan, 107 Wiggins Rd., Saskatoon, Saskatchewan S7N 5E5 Canada.
authors.forename: Benjamin Wc
authors.initials: BW
authors.lastname: Rosser
authors.affiliation: Current Address: School of Physical Therapy, University of Saskatchewan, 1121 College Drive, Saskatoon, Saskatchewan S7N 0W3 Canada.
authors.forename: Soo Y
authors.initials: SY
authors.lastname: Kim
keywords: Elderly; Foot; Intrinsic foot muscle; Muscle fiber; Myosin heavy chain; Quadratus plantae