Muscles

• Muscles are a soft tissue that contract and relax to bring about movement.
• A muscle consists of two filaments: a thick protein filament made of the protein myosin and a thin filament composed of actin which is also a protein.
• When movement occurs, the thin actin filaments move between the thick myosin filaments, lengthening and shortening the length of the sarcomere.
• A sarcomere is the basic unit of muscle fibre.
• Slow twitch muscle fibre is characterized by slow, sustained contractions, endurance sports, and has many mitochondria for more energy released from respiration, large oxygen and glucose stores, and does not tire quickly.
• Fast twitch muscle fibre is characterized by rapid intense contractions, short burst activities such as sprints, fewer mitochondria for energy produced from anaerobic respiration, few capillaries for lower blood supply, and tires easily and quickly.