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 ( % of max strength) –High Volume ( 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