adaptations to resistance training - chapter 11

muscle has innate _____ which can change in size & strength

plasticity

this plasticity does what?

balance between protein synthesis and protein breakdown

muscle hypertrophy

increase in muscle size which is due to an increase size of the fibers (NOT the number of fibers)

muscle atrophy

decrease muscle size which is due to either fiber atrophy or fiber loss

synthesis

muscle protein synthesis (MPS), the biological process by which the body creates new muscle proteins from amino acids

increase in muscle size =

increase muscle strength

3-6 months of RT does what?

- 25-30% increase strength

- 50% early strength gains due to "learning" (effective force production and true maximal movement

what is not the only factor involved?

neural system plays a role

short term (8-10 weeks)

- increase 1RM that is due to increase voluntary neural activation

long term (more than 10 weeks)

fiber hypertrophy which also has a net increase in protein synthesis (takes time to occur)

cannot have increase in strength without an adaptation in ____ control

neural

neural strength gains result from changes in:

- increase neural drive (synchronization) which then leads to an increase in motor units firing

- increase rate coding (frequency of discharge) which then leads to reaching tetanus faster

- decrease inhibitor impulses

- activation of agonist and antagonist muscles

- morphology of NMJ

some combination of improved motor unit synchronization & recruitment =

strength gains

normal motor unit recruitment =

asynchronous (not all motor units are engaged at the same instant)

synchronous recruitment leads to....

strength gains

RT leads to.....

synchronous recruitment

synchronous recruitment does what?

- increase force of contraction

- increase rate of force development

- steadiness of force

inhibitory mechanisms lead to what?

GTO's

GTO's:

- inhibition with high tension

- prevent damage to bones and tendons

training leads to....

decrease inhibitory impulses that can have an increase force generation

hypertrophy =

increase muscle size

what are the two types of muscle hypertrophy?

1. transient

2. chronic

transient hypertrophy

- after an exercise bout

- due to edema formation from plasma fluid (pump)

- temporary (only lasts a few hours)

chronic hypertrophy

- long term

- reflects structural changes in muscle

- fibers are affected

muscle atrophy =

decrease protein synthesis, increase in protein breakdown

immobilization:

- 6 hrs: decrease protein synthesis which initiates muscle atrophy

- 1 week: decrease size, neuromuscular activity, and strength (3-4% per day)

- reversible effects on type 1 and type 2 fibers (type 1 affected more than type 2 and a decrease in CSA)

strength can be maintained over ____ weeks with decrease training frequency from 3 days/week to 1 day/week

12

resistance training

increase muscle strength & muscle hypertrophy

hypertrophy vs atrophy = balance between.....

protein synthesis & protein breakdown

increase of muscle strength is dependent on 2 systems

muscular system (muscle fibers) & neural system

with resistance training, muscle fibers increase in ____?

cross sectional area

RT =

increase protein synthesis

muscle protein content always changing....

- during exercise = decrease synthesis, increase breakdown

- after exercise = increase synthesis, decrease breakdown

hormones =

elevated post-exercise

what does testosterone facilitate?

fiber hypertrophy (natural vs synthetic, large does steroid + RT = large increase muscle mass & strength)

what other hormones are elevated?

growth hormone (GH)

insulin-like growth factor 1 (IGF-1)

satellite cells

stems cells involved in muscle regeneration

what are satellite cells activated with?

muscle injury (cascade response ending with satellite cells fusing to existing/new myofibers)

provide additional ____ within the muscle fiber

nuclei

true or false: muscle is multinucleated?

true

added genetic machinery is necessary to ____ muscle protein content and facilitate hypertrophy

increase

what are the biochemical changes with RT

- metabolic

- hormone

- enzyme changes

metabolic

increase creatine, phosphate, ATP, glycogen

hormone

- increase testosterone, GH

- NOT REQUIRED to increase muscle strength/size

enzyme changes

little to no change in activity of ATP-PCr and glycolysis

what type of change is made in myoglobin content?

little to no change

what happens with the mitochondrial function?

- increase biogenesis

- increase fusion, decrease fission (may improve mitochondrial function)

capillary content

- increase # capillaries which leads to an increase nutrient supply which then leads to contributing to total muscle size (increase bodybuilders, decrease power & weight-lifters, linked to intensity & volume of training

- slow change (12 weeks)

what are the cardiovascular effects?

HR

BP

Cardiac Dimensions

HR

little to no change (increase parasympathetic & decrease sympathetic

BP

little to no change

cardiac dimensions

LV hypertrophy (strengthened myocardium which leads to stronger contraction which leads to increase SV

connective tissue

- strengthened ligaments, tendons, and fascia

- proliferation around individual muscle fibers which leads to a thickening and strengthening of connective tissue

- happens quickly

bone mineral content

increases slowly (6-12 months)

short term vs. long term gains in muscle strength which leads to neural adaptation or hypertrophy?

neural adaptation

muscular atrophy which leads to protein balance, fibers affected, permanent?

- protein breakdown > protein synthesis

- type 1 affected more than type 2 (but both are impacted)

- can recover

substantial or minor drivers of hypertrophy

biochemical changes = minor

cellular changes = minor

cardiovascular changes = minor

supporting structure changes = minor

____ intact, high quality protein is sufficient to maximize the anabolic response to resistance exercise

20g

protein intake

- increase protein synthesis after RT

- ingestion of 20g protein after RT for muscle growth

- 1.6-1.7g protein/kg body weight/day for increase muscle mass

- small doses (20g) every 2-3 hours recommended for protein synthesis

true or false: muscle soreness can be felt at only certain times

false, muscle soreness can be felt at any time

from exhaustive or high-intensity exercise....

especially common the first time performing a new exercise or returning to exercise

there are 2 types of muscle soreness. name and describe them.

1. acute soreness - during and immediately after exercise

2. delayed-onset muscle soreness (DOMS) - 1-2 days after exercise

acute muscle soreness

- during and/or immediately following strenuous exercise (accumulation of metabolic byproducts (H+) (tissue edema (plasma fluid into interstitial space)

- edema which leads to acute muscle swelling

- disappears within minutes to hours

DOMS occuries how many days after exercise bout?

1-2 days

DOMS ranges from __1__ to __2__, restrictive pain

1. stiffness

2. severe

major cause:

eccentric contractions

- (ex) pain from running on level ground < pain from downhill run

- NOT caused by increase blood lactate concentration (why? because lactate can be used as a fuel!

structural damage indicated by muscle enzymes (ex. CK) in blood which does what?

- concentrations increase 2-10x after heavy training

- onset of DOMS parallels onset of increase muscle enzymes in blood

sarcomere's Z discs are the anchoring points of contact for ____ proteins

contractile

muscle damage prompts____

hypertrophy

DOMS does what?

decrease muscle force generation

loss of strength from 3 factors:

1. physical disruption of muscle

2. failure in excitation-contraction coupling (appears to be most important)

3. loss of contractile protein

what are the 3 strategies to reduce DOMS?

1. minimize eccentric work early in training

2. start with low intensity and gradually increase

3. start with high intensity, exhaustive training (soreness is bad at first but is much less later on)

what is muscle hypertrophy? what is muscle atrophy? for each, what does it mean for the balance between protein synthesis and breakdown?

a. muscle hypertrophy = when muscle gets bigger (this happens when protein synthesis > protein breakdown (your body builds more muscle that it loses))

b. muscle atrophy = when muscles get smaller or weaker (this happens when protein break down > protein synthesis (your body loses more muscle than it builds))

what is a reasonable expectation for percentage strength gains following a 6-month training program? what can these increases be attributed to?

a. neural adaptations (your brain and nerves get better at activating muscles)

b. muscle hypertrophy (your muscles get bigger and stronger)

what changes in neural control result in strength gains with resistance exercise?

a. more motor units activated (you use more muscle fibers at once)

b. better synchronization (muscle fibers work together more smoothly)

c. reduced inhibition (your body allows stronger contractions)

d. improved coordination (movements become more efficient)

what happens with motor unit recruitment with resistance exercise? autogenic inhibition?

a. motor unit recruitment: you learn to activate more motor units and fire them more efficiently, which increases strength

b. autogenic inhibition: this decreases, meaning your body becomes less likely to limit force production, allowing your muscles to contract harder without the nervous system holding them back

what are the different types of hypertrophy? what is the reason behind each one?

a. myofibrillar hypertrophy (reason: increase in the number and size of myofibrils (the contractile parts of muscle fibers) (result: muscles get stronger and denser)

b. sarcoplasmic hypertrophy (reason: increase in the sarcoplasm (fluid and energy stores inside the muscle cell) (result: muscles get larger in size, but not as much strength gain

what happens within a muscle fiber during muscle hypertrophy?

during muscle hypertrophy, inside the muscle fiber:

- more myofibrils (contractile proteins) are made

- existing myofibrils get thicker

- more actin and myosin (protein filaments) are added

- the muscle fiber gets bigger and stronger overall

what is the critical factor for short term increases in muscle strength? for long term increases?

- short term increase: come mainly from neural adaptations (your brain and nerves learn to activate muscles better)

- long term increases: come mainly from muscle hypertrophy (your muscles actually grow bigger)

what happens to protein synthesis/breakdown with atrophy? how are the different muscle fibers affected?

with atrophy:

- protein breakdown increases, and protein synthesis decreases, so muscle mass is lost

- type 1 (slow-twitch) fibers shrink slowly

- type 2 (fast-twitch) fibers shrink faster and more

what are the biochemical and cellular changes that occur with resistance training?

- increased protein synthesis leads to building more muscle proteins

- more myofibrils and contractile proteins (actin and myosin)

- more enzymes for energy production (especially anaerobic ones)

- stronger connective tissue (tendons and ligaments)

- more stored ATP, creatine phosphate, and glycogen in the muscle

what are the capillary and cardiovascular effects of resistance training?

- capillaries: the number of capillaries around each muscle fiber may stay the same or increase slightly, but because the fibers get bigger, capillary density can decrease

- cardiovascular system: the heart gets stronger, especially the left ventricle wall, improving blood pressure control and force of contraction but endurance capacity doesn't increase much

how does protein and amino acid supplementation affect protein synthesis? does timing matter?

- protein and amino acid supplements help increase protein synthesis especially when combined with resistance training

- timing matters: taking protein soon after exercise (within about 30-60 minutes) helps maximize muscle repair and growth

muscle ____ requires both muscular and neural systems

hypertrophy

neural adaptations occur ____ muscular adaptations

before

muscle atrophy results in what?

reversible muscle loss

increasing muscle protein synthesis is the ____ ____ factor of muscle hypertrophy

most important

20g protein + exercise leads to greater ____ in protein synthesis than exercise along with no supplementation

increase

muscle soreness is due to ____, not lactate buildup

DOMS

what immediate changes occur in HR, SV, and Q when you begin exercise? what drives them?

a. HR and contractility increase; together, increase HR + increase SV = increase Q to meet O2 demands

b. central command signals from motor cortex leads to increase in SNS activity and decrease vagal tone

why does stroke volume eventually plateau around 40-60% VO2max in most individuals?

higher intensities lead to decrease ventricular filling time which leads to decrease EDV (preload)

how does steady-state HR reflect aerobic fitness?

a lower steady-state HR at the same workload indicates higher efficiency

oxygen uptake depends on how much blood the heart pumps (Q) and how much O2 muscles extract from that blood; VO2 = HR x SV x (a-v)O2 difference. what principle is being described?

fick principle

how does ventilation change as intensity increases? what causes the ventilatory threshold?

a. ventilation rises proportionally to workload until the ventilatory threshold

b. when CO2 and H+ accumulation from lactate buffering stimulate hyperventilation

what are the primary causes of fatigue during short, high-intensity exercise vs. long-duration endurance exercise?

a. short/intense = decrease ph from excess H+ ions inhibits contraction

b. long/endurance = glycogen depletion limits ATP resynthesis, forcing slower fat metabolism ("hitting the wall")

after 8-12 weeks of aerobic training, what cardiovascular and muscular changes explain improved performance at the same workload?

a. CV: increased HR rest/submax, increased SV, increased Qmax, increased blood volume, increase capillarization

b. muscle: increased mitochondria, increased oxidative enzymes, increased a-vO2 difference leads to greater efficiency and O2 extraction

short-term integration of strength gains =

our nervous system learns to communicate better with our muscles that lead to increased strength

long-term integration of strength gains =

increased muscle size that leads to increased muscle strength

increased motor unit recuitment r

your body learns to activate more motor units (a-motor neuron + the muscle fibers it innervates) simultaneously

improved firing rate (rate coding)

a. neurons send action potentials more rapidly and frequently, increasing the rate of force development

b. faster firing = more frequent muscle twitches summating into smoother, stronger contractions (from twitch to summation to tetanus)