skeletal muscle adaptation

in the first 3 months of a strength program, a person can see

25-100% increase in strength gains via neural adaptations

electromyography

sum of all action potentials occurring within the recording area of an electrode - measures neural drive for muscle activation

a lot of factors alter EMG findings

consider various factors with use, and normalize data for meaningful interpretation of EMG amplitude

normalizing EMG

comparison to EMG amplitude during maximal voluntary contraction (MVC) OR to electrically evoked response (M wave)

can use EMG to determine exctiability of

skeletal muscle (mwave), spinal pathways (H reflex), supraspinal pathways (voluntary activation), and fatigability of neuromuscular system

greater neural activity to the muscle, at the same intensity can show

increased MU activation, crossbridges formed and strength

increased neural activation will also

increase motor unit firing rate and synchronization, and reduce inhibitory reflexes (GTO) to permit greater strength

other neural changes with increased resistance taining

activation of cortical areas associated with movement and planning (stayed more active even at rest), crossover associated with training unilaterally and inducing some changes on contralateral limb (not equal but can help minimize muscle mass loss with immobilization)

muscles increase in cross sectional area is due to

hypertrophic changes increasing amount of muscle fibers and size

hyperplasia

creating new muscle cells (not the primary contributer to increased CSA)

movement stimulates protein synthesis

if you're taking in enough dietary protein

movement stimulates protein breakdown

via eccentric activation causing damage

protein dietary needs

1.7g/1kg of BW for optimal protein synthesis within the 1st 1-2 hours of exercise

rest time is essential fro protein synthesis to

allow adaptation and building of proteins

satellite cell

specialized stem cell that is a muscle cell precursor - increase with training

satellite cells contain a lot of

nuclei housing RNA and DNA responsible for protein synthesis - satellite cells fuse with muscle fibers and the increased number of nuclei allow for increased protein synthesis

if there is detraining from a hypertrophic state

nuclei remains in the atrophied cells - "muscle memory"

the mechanical stimulus of muscle activation and damage of exercise

activates a cascade of intracellular signaling and the release of mTOR which kickstarts protein synthesis

mTOR is activated by

presence of AA's and the release of insulin

hypertrophy is when there is more synthesis than breakdown

increasing contractile protein and cross bridges, which increase strnegth

stimulatory threshold for protein syntehsis

>60% 1RM

increased number of sarcomeres in series

increased cross sectional area

hypertrophy occurs in

all 3 fibers types but type 2x FG fibers have greatest increase in CSA (adaptations are influenced by genetics, age, sex, and training protocol)

neuromuscular adaptations to resistance training include increases in

total contractile protein, size and # of myofibrils per fiber, and amount of CT surrounding muscle fiber

male-female resistance training adaptation comparison

greater % change in females than males (baseline is lower)

older adult resistance training adaptations

greater % change in older adults and frail elderly - dont underdose

muscle function adaptations to resistance training

increased strength, endurance and power

for LE exercises, studies show

3 sets is more effective than 1 set

for UE exercises, studies show

1 set is just as effective as 3 sets

muscular adaptations to aerobic endurance training programs

increase in slow oxidative fiber size, possible transition in FG to FOG (metabolic change)

concurrent training

combining both resistance training and aerobic training in same session and time period

concurrent aerobic and strength training shows

less hypertrophy and less power gains - if necessary do periodization and split training into different days

rest time required for adaptation

24-48 hours depending on intensity, >96 will result in atrophy and loss of benefits