how muscle grows
DESCRIPTION
How Muscle Grows. Chapter 2 Read pgs: 29-33, 35-38, 40-44. 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. Increased muscle size - PowerPoint PPT PresentationTRANSCRIPT
How Muscle Grows
Chapter 2
Read pgs: 29-33, 35-38, 40-44
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
Benefits of Resistance Training
• 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
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
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.
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
Neural Adaptations to RT
• Strength increases during initial few weeks of an RT program
• Neural function improved, along with coordination, & agonist/synergist
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
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
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
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)
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.
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
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
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
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
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
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
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