MUSCLES CONTRACT. “All skeletal muscle, including mimetic musculature, works by getting shorter, or contracting. Each muscle is made up of smaller units that work together to contract. Muscles consist of packaged units called ‘fascicles’, collections of muscle fibers enveloped by connective tissue. Each muscle fiber (or myofiber) in turn consists of bundles of myofibrils, which are made up of many filaments of contractile proteins. One of those contractile proteins is myosin.”
http://onlinelibrary.wiley.com/doi/10.1111/joa.12440/full