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How Muscle Grows

How Muscle Grows

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How Muscle Grows

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  1. How Muscle Grows Chapter 2 Read pgs: 29-33, 35-38, 40-44

  2. 2 Ways a Muscle can Grow • Hypertrophy- an increase in the size of individual muscle fibers • Primary means for muscle growth • Hyperplasia- an increased number of muscle fibers • Controversial

  3. Increased muscle size Improves muscle strength Improves bone health Improves athletic performance RT benefits both men & women Stay healthy & offset natural aging process Sarcopenia Osteopenia Osteoporosis Benefits of Resistance Training

  4. Fears of getting “too big” • Women have fewer muscle fibers, esp. in upper body • Hormone (testosterone) level is lower in women • Difficult to develop large muscles without use of anabolic drugs

  5. Foundation for Muscle Growth • 1. Muscle must be stimulated • Well designed RT-program • 2. Well balanced diet (adequate calories) • Increasing muscle size requires energy • If either of these two principles are ignored, muscle will not adapt.

  6. Foundation for Muscle Growth • Carbohydrates, proteins & fats serve as building blocks to repair & remodel muscle. • Timing of nutrient intake is important • Sleep & a healthy lifestyle are important

  7. Neural Adaptations to RT • Strength increases during initial few weeks of an RT program • Neural function improved, along with coordination, & agonist/synergist

  8. Muscle Stimulus • If Goal is HYPERTROPHY: • Moderate to heavy loads (70 - 85% of max strength) • High Volume (8 - 12 reps for 3 or 4 sets) • This program stimulates greater acute increases in natural occurring anabolic hormones in the body

  9. Muscle Stimulus • Shorter rest periods = greater metabolic stress (increased lactic acid in blood), stimulating hormone release. • This stimulates muscle protein synthesis & increased muscle size • 1-2min rest periods recommended

  10. Process of Muscle Growth • Motor units must be activated • Adequate EX intensity • Size Principle • Low-intensity (type I) exercises vs. High-intensity (type II) exercises to increase muscle size

  11. Hormone Responses to RT • RT sends signals to all organ systems of the body • The systems then support muscle’s ability to produce force & contribute to recovery & growth of muscle • Cardiovascular system • Endocrine system (epinephrine, testosterone) • Immune system (tissue repair)

  12. Hormone Responses to RT • Epinephrine (adrenaline) helps muscles produce force. • Testosterone and growth hormone stimulate muscle protein synthesis, sending signals to the muscle to regenerate & grow. • RT increases anabolic hormones in blood during & approx. 1-hr post ex, allowing body to rebuild & add muscle at that time.

  13. Hormone Responses to RT • RT stimulates release of growth hormone from pituitary gland in brain • GH travels in blood & stimulates prod. Of insulin-like growth factor in the liver & muscles • This IGF-I binds to a muscle cell’s receptor, triggering increase in production of proteins

  14. Hormone Responses to RT • Maximizing hormonal response to exercise = increase in muscle size (hypertrophy) • Workouts that are structured using high volume & intensity, short rest periods, & that use large muscle mass will maximize body’s natural capacity to stimulate muscle growth -Denmark study in 2001

  15. Muscle Damage & Immune Response • Microscopic damage occurs • Leads to inflammation & swelling,soreness • But, this provides stimulus for growth • How? The immune response to damage. • WBC’s cause increase blood flow to muscle • Blood carries 02 & nutrients to muscle and helps remove waste product

  16. Protein Synthesis • Acute increase in anabolic hormonesin muscle stimulates increase in protein synthesis • Actin & Myosin are contractile proteins located in muscle cell • Increased # of contractile proteins = hypertrophy & strength/power

  17. Protein Synthesis • Amino acids cross cell membrane & enter skeletal muscle • Increasing amino acid intake post-RT can increase availability of aa’s to assist in protein synthesis

  18. Important Factors for Protein Synthesis with RT • Amino acid availability • Timing of post-RT intake (sooner is better) • Hormonal regulation • Mechanical stress (intensity, volume of RT) • Cellular hydration

  19. Protein Synthesis • To maximize protein synthesis: • Eat a meal soon after exercise • Meal should contain carbohydrate & protein • Carbohydrate will replace fuel stores (glycogen) in muscle • Protein will facilitate repair & building of muscle