Each muscle fiber consists of a cross-banded structure that is further divided into myofibrils that contain thick (myosin) and thin (actin) myofilaments, which give muscle its stripe appearance.

Correspondence to Dr Kimberly G Harmon, Hall Health Sports Medicine Clinic, Box 354410, University of Washington, Seattle, WA 98195, USA; kharmon{at}u.washington.edu If you wish to reuse any or all of ...