Chapter 14: The Physiology of Resistance Training Flashcards
Muscular strength
maximal force a muscle or muscle group can generate (1-RM)
Muscular endurance
ability to make repeated contractions against a submaximal load
High-resistance training (heavy weight, low reps) results in
gains in strength
Low-resistance training (lighter weight, high reps) results in
gains in endurance
Strength training results in
increase in muscle size and strength
Strength gain in short term training (2-8 weeks)
Neural adaptations are responsible for early gains in strength gains
Strength gain in long-term training (20+ weeks)
Increase in muscle size (hypertrophy) and fiber specific force are most important for long-term gains in strength
How long does it take for muscle hypertrophy to occur?
Muscle hypertrophy increases during months or years of training
but, high-intensity resistance training can result in hypertrophy with 10 sessions (3 weeks)
Compare endurance and resistance training induced CNS adaptations
endurance training —> no carry over effect of training to contralateral side of body
resistance training —> if one arm is trained, then the untrained contralateral arm receives strength gains (phenomenon called “cross-education”)
Cross-education
trained side receives gains via hypertrophy and neural adaptations
untrained side receives gains via neural adaptations
Neural adaptations in strength training include
- increased motor units recruited
- increased firing rate of motor units
—–increased frequency of depolarization result in increased force production - increased motor unit synchronization
—-simultaneous recruitment of numerous motor units resulting in increased force production - improved neural transmission across neuromuscular junction
increased muscle fiber specific tension in type 1 fibers from resistance training due to
increased calcium sensitivity, which increases the number of cross bridges bound to actin
Hypertrophy
increase in muscle fiber cross-sectional area
size of type I and II fibers increase but size of type II fibers increase more
Hypertrophy is due to
increased actin and myosin because of the addition of sarcomeres in parallel of existing sarcomeres
Hyperplasia
increase in muscle fiber number
- evidence supporting hyperplasia in animal studies but no conclusive evidence this happens in humans
- even if hyperplasia does occur in humans, it’s contribution to muscle mass is likely small
Resistance training promotes changes in muscle fiber type
fast-to-slow shift in fiber type
from type IIx to IIa
- 5-11% change following 20 weeks of training
- no increase in type I fibers
lesser extent than endurance training
Resistance training improves antioxidant capacity how?
100% increase in key antioxidant enzymes following 12 weeks of training
Can resistance training improve muscle oxidative capacity and increase capillary number?
studies show conflicting results on mitochondrial content and capillary number… because of different frequency and duration of training
Long-term, high frequency (3d/wk), high volume (high reps) training resulted in
small increases in muscle oxidative capacity and capillary number
Muscle protein synthesis increases _____ 1 to 4 hours after a single bout of resistance training in trained and untrained individuals
50-150%
How long does protein synthesis remain elevated?
30 to 48 hours, but depends on training status
– elevated longer in untrained individuals
Key factors that contribute to resistance training-induced increases in muscle protein synthesis
- mRNA increases, resulting in protein synthesis at the ribosome
- ribosomes increase in number and elevate muscle’s protein synthesis capacity
- activation of the protein kinase “mechanistic target of rapamycin” (mTOR) is the key factor accelerating protein synthesis following a bout of resistance training
Resistance training induced fiber hypertrophy results in
a parallel increase in muscle fiber size and number of myonuclei
increases myofibrillar proteins and fiber cross sectional area
Resistance training activates satellite cells to
divide and fuse with adjacent muscle fibers to increase myonuclei
- addition of new myonuclei fibers increases protein synthesis in larger muscle fibers-essential to achieve maximal hypertrophy
Resistance training induced increases in myonuclei results in
a constant ratio between number of myonuclei and size of muscle fiber
myonuclear domain remains constant
Resistance training-induced satellite cell activation in older individuals
is blunted which limits resistance training-induced muscle hypertrophy
testosterone, insulin-like growth factor-1 and growth hormone are linked to
mTOR activation and can increase muscle protein synthesis
though, these can occur independent of these hormones
a bout of resistance training increases circulating levels of
testosterone, IGF-1 and growth hormone
How much of the differences in muscle mass between individuals is due to genetic variation?
approximately 80%
How many different genes are major contributors to muscle mass?
47
Many hypertrophy-linked genes are directly linked to
the mTOR pathway and are activated via resistance training
large differences exist in the magnitude of resistance training-induced skeletal muscle hypertrophy due to
variations in ability to activate specific “protein synthesis genes in skeletal muscle in response to resistance training
Low responder
low genetic potential for hypertrophy
Moderate-responder
moderate genetic potential for hypertrophy
High-responder
high genetic potential for hypertrophy
Do anti-inflammatory drugs impact resistance-training-induced hypertrophy?
- Animal studies suggest that these drugs blunt resistance training-induced muscle hypertrophy
- However, recent human studies reveal that these drugs do not negatively impact strength gains in humans
Short answer, no.
How much of a decrease in strength is there following 30 weeks of detraining?
there is a slow decrease in strength
31% decrease
Small changes in fiber size during detraining
- Type I fiber size– 2%
- Type IIa fiber size– 10%
- Type IIx fiber size– 14%
The slow decrease in strength with detraining is primarily due to
nervous system changes
Retraining results in
rapid regain of strength and muscle size
– within 6 weeks after resuming training
Muscle memory
the ability for a rapid recovery
– the mechanism responsible for muscle memory remains controversial
Recent research suggests that muscle memory is due to
resistance training-induced increases in myonuclei in the trained fibers that are not lost during detraining
– maintaining myonuclei provides advantage in rapid protein synthesis upon retraining
Prolonged periods of muscle inactivity or unloading (bedrest, cast, space flight) results in
after 7 days…
20 to 30 days…
skeletal muscle atrophy
7 days—> 7 to 10% loss of muscle mass
20-30 days —> 15 to 20% reduction in muscle fiber size
Conservation of muscle mass is dependent upon
balance between protein synthesis and rates of protein degradation.
Inactivity-induced muscle atrophy occurs due to
decrease in muscle protein synthesis
increase in muscle protein breakdown
Increased _______ promotes muscle atrophy during prolonged inactivity by depressing protein synthesis and increasing degradation
production of free radicals
– results in oxidative stress
Strength training increases _____ whereas endurance training does not.
muscle fiber size
Many studies conclude that concurrent strength and endurance training has what effect?
impairs strength gains, compared to strength training alone
– the impact of concurrent training on strength gains depends on intensity, volume, and frequency of endurance training
