Muscular system

• Voluntary muscles are under our conscious control so we can move these muscles when we want to
• Endurance cyclists need a high percentage of type I fibres so that their muscles can work for the duration of a race without getting tired
• Sprinters need a high percentage of type II fibres which allow their muscles to contract very quickly. Fast muscle contractions give runners power and enable them to hit a high speed over a short distance
• However, type 2 muscle tire very quickly, meaning sprinters are not able to run at this speed for very long
• Muscles cause movement by contracting across joints. Muscles are attached to the skeleton by tendons in two places:

  • the origin
  • the insertion
• The origin is the end of a muscle which is attached to a fixed bone. The insertion is the other end of the muscle that is attached to the bone which moves
• Isotonic contraction involves the muscle producing tension and controlling the speed of the muscular contraction
• Isotonic concentric contraction involves the muscle shortening. The origin and insertion of the muscle move closer together and the muscle becomes fatter
• Isotonic eccentric contraction involves the muscle lengthening whilst it is under tension. The origin and the insertion move further away from each other
• Isometric contraction involves a muscle producing tension but staying the same length. This occurs when the body is fixed in one position.
• Muscles contract isometrically to hold a gymnast in the crucifix position and aren't changing length. When the isometric contractions end, isotonic contraction will occur
• When a footballer prepares to kick a football, their hamstrings contract to flex the knee while the quadriceps lengthens to allow the movement
• Slow Twitch:

  • make use of O2
  • energy provided aerobically
  • small amounts of power
  • highly resistant to fatigue
  • high levels of red blood cells (mitochondria)
  • relatively slow contraction speed
• Fast Twitch:

  • work anaerobically
  • limited to no use of O2
  • high amounts of power created
  • low resistance to fatigue
  • low levels of red blood cells
  • quick contraction speed
• Fast Twitch function: For fast, powerful events where fatigue happens quickly
• Slow Twitch function: For events that r aerobic and at a relatively low intensity so that fatigue is not a problem