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Muscles, Muscle Contraction and Strength

Muscles, Muscle Contraction and Strength. How Muscles Work. The muscles arranged along the skeletal frame of the body, always act as a group rather than contracting individually. Therefore the movements performed about a joint are produced by several muscles, with different roles.

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Muscles, Muscle Contraction and Strength

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  1. Muscles, Muscle Contraction and Strength

  2. How Muscles Work • The muscles arranged along the skeletal frame of the body, always act as a group rather than contracting individually. Therefore the movements performed about a joint are produced by several muscles, with different roles.

  3. How Muscles Work ROLES: • Agonists: muscles that work together to perform a movement (ex. Bicep, • Antagonists: muscles that during motion act in opposition to the agonists • Stabilizers: smaller muscles which contract to anchor, or steady, a bone so that the prime movers have a firm base to pull on

  4. How Muscles Work Types of Muscular Contraction: • Concentric (positive): contractions in which the muscle length shortens. • Eccentric (negative): contractions in which the muscle length increases • Isometric (static): the muscle develops tension without changing its length

  5. How Muscles Work Energy Sources for Contraction: • ATP is the fuel that supplies energy to our muscles. (ATP  ADP + P + energy) • There is a limited amount of ATP stored in the muscle cells thus they must continuously be restored.

  6. How Muscles Work The Three Energy Systems: Anaerobic Systems (No O2) • ATP-CP system • Lactic Acid System Aerobic System (O2) • The Oxygen System (O2)

  7. ENERGY SYSTEMS ATP – CP (Anaerobic) In addition to ATP, small amounts of creatine phosphate (CP) are stored in the muscle. It can restore ADP to ATP This system can only restore energy for 8-10 seconds. It takes 60 sec to restore 70% of the CP and 3-5 minutes to restore 100% of the CP.

  8. ENERGY SYSTEMS The Lactic Acid System (LA): For intense events between 90-120 seconds. The LA system breaks down glycogen which is stored in the muscle and liver cells, releasing energy to reconvert ADP + P to ATP. However due to a lack of O2 LA builds up. This LA causes fatigue, which eventually leads to cessation of exercise.

  9. ENERGY SYSTEMS The Lactic Acid System (LA): It takes 30 min of rest to remove 50% of the LA. However, this time can be reduced to 10 min with active rest. Restoration of the glycogen takes 24-48 hours. Depending on the intensity and repetition of the activity and the fitness level of the person.

  10. ENERGY SYSTEMS Aerobic System: Predominant energy source for activities 2min-3hours. Breaks down glycogen in the presence of O2. Due to the O2 little lactic acid is produced with the aerobic system. But instead C O2 and H2O. The rate at which the ATP is replenished is limited by ones aerobic capacity. (heart and respiration capacities)

  11. Muscle Fiber

  12. Muscle Fiber Fiber Types: Type I (slow-twitch): aerobic 50% Type IIa (fast-twitch): oxidative anaerobic 25% Type IIb (fast-twitch): non-oxidative 25% Your ability to use specific fiber types is dependant upon your nervous systems ability to recruit them and how you have trained them .

  13. Muscular Adaptation Adaptation is the sum of modifications brought about by the systematic repetition of exercise. Hypertrophy: enlargement of muscle size Fiber Type: Type IIa acts as Type I or Type II depending on training Nervous system: ability to recruit fibers increases with training as does coordination

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