Lesson 6 - General Effects of Resistance Training on Skeletal Muscle
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What causes strength to increase due to resistance training?
• changes in the nervous system and increases in muscle mass
How does the nervous system change in response to resistance training?
• increased neural drive • decreased inhibition • increased spinal motor neuron excitability • improved motor unit recruitment and discharge rate (more efficient) • improved coordination of motor units
When do most neural adaptations occur and contribute to most of strength gain?
4-6 weeks
What is hypertrophy?
increase in muscle fiber cross-sectional area making more contractile proteins per fiber
What is the primary mean of increased strength with long-term resistance training?
hypertrophy
How long does it take for hypertrophy to occur with a high intensity program?
3 weeks
Which muscle fiber type increases in size?
both type 1 and 2, with type 2 having greater capacity for change
What is the reason for the increase in muscle size/hypertrophy?
addition of sarcomeres
What is hyperplasia?
an increase in the number of muscle fibers in a given muscle
Does hyperplasia occur in humans?
not enough evidence supporting or negating
What type of fiber shift is typically seen from resistance training?
type 2x to type 2a due to change in myosin isoform and reduced ATPase activity for better efficiency fast to slow
What is mechanotranduction?
process by which high mechanical stress is translated to chemical signals that ultimately lead to increased production of contractile protein and muscle growth
What does mechanotransduction rely on?
activation on mechanoreceptors that mediate mammalian target of rapamycin complex 1 and other aerobic pathways
What muscle fiber has the most satellite cells?
type 2 fibers
What does the activation of satellite cells do with hypertrophy?
donate their nuclei to muscle fibers and increase number of nuclei per fiber helping in muscle repair
What stimulates satellite cells?
muscle damage
What percentage of 1RM can induce hypertrophy if performed to fatigue?
30% 1RM
What does low load reps to fatigue trigger?
• increased recruitment of larger muscle fibers • increased accumulation of metabolites due to shift to anaerobic metabolism, stimulate hypertrophy • increased production of IGF-1 and growth hormone
How long of rest should you take for hypertrophy?
short rest
How does decreasing inter-set intervals (rest time) increase metabolic stress and hypertrophy?
decreases training volume and mechanical load
What are the 4 main mechanisms of hypertrophy?
• mechanotransduction • activation of satellite cells • hypertrophy by induced metabolic stress • modulation of mechanical load and metabolic stress
What are the primary hormones that affect adaptation to resistance exercise?
testosterone and growth hormone
What does testosterone do?
• amplify growth hormone and insulin like growth factor 1 (IGF-1) release and action • increases muscle force production by interacting with nervous system
What do repeated session of resistance training do to the temporary increase in testosterone during exercise?
increases frequency and amplitude