Adaptations to Resistance Training

muscle strength

maximal force that a muscle group can generate

• 1-RM

muscular endurance

ability to make repeated contractions agains a sub-maximal load

high vs low resistance training

high: 6-10 reps till fatigue

low: 30-40 reps till fatigue

how does aging generally affect muscle compositions and around what age does this occur

loss of both muscle mass and strength

• greatest decline at > age 50

• atrophy type II fibers

• reduce # of both type I and II fibers

how does resistance training affect muscle composition

changes nervous system and muscle fiber size/function

• increase muscle fiber specific tension

• increase muscle mass

what is responsible for early gains in strength

neural adaptations - first 2-8 weeks

list the 4 neural adaptations

increase # of motor units

• more motor units allow us to send more signals down the T tubules to release calcium

increased firing rate of motor units

• more frequency = more power produced

increase motor unit syntonization

• motor units fire closer to the same time as one another

improve neural transmission across NMJ

• neuron releases acetylcholine, travels across cleft and riches muscle

resistance training increases muscle fiber specific tension in which type of muscle fiber

type 1

• due to increase calcium sensitivity - resulting in greater number of cross bridge bound to actin

hyperplasia

increase number of fibers

hypertrophy

increase cross sectional area of muscle fibers

how does training affect muscle protein synthesis

increase

what key factors contribute to resistance training induced increases in muscle protein synthesis

• mRNA increase resulting in protein synthesis at ribosome

• ribosome increase in number and elevate muscle protein synthesis capacity

• activation of mTOR (this is the key factor)

what 2 molecules stimulation mTOR activation for muscle protein synthesis

phosphatidic acid (PA) and Rheb

describe the role of TSC 2 in this photo when

At rest, TSC inhibits Rheb so that we do not activate mTOR

when we exercise, ERK inhibits the inhibitor, TSC2 so that we do activate Rheb and mTOR to get protein synthesis

which hormones are linked to mTOR activation and have POTENTIAL to increase muscle protein synthesis (though not absolutely necessary)

insulin like growth factor (IGF-1)

growth hormone

do NSIDS impact resistance training induced hypertrophy

does not negatively impact, may affect inflammatory response

what is the role of satellite cells in resistance training induced hypertrophy

resistance training activates satellite cells to divide and fuse with adjacent fibers to increase myonuclei

• additional myonuclei is likely required to support protein synthesis in larger muscle

resistance training results in parallel increase in what 2 things

muscle fiber size and number of nuclei

approximately 80% of differences in muscle mass between individuals is due to ___

genetic variation

• influences the magnitude of resistance training induced hypertrophy

• many hypertrophy linked genes are directly linked to the mTOR path

which is fastest to detrain: endurance or strength training

endurance

why do type Iix fibers detrain quickest compared to type I

we always recruit type I first so that will not detrain much unless we are on bedrest

Mechanisms to explain impairment of strength
gains resulting from concurrent training

neural factors

• impaired motor recruitment

overtraining

depressed protein synthesis

• interference from endurance training