Exam 2: Resistance Training Adaptations

Dr. Schneider - Fall 2023

hypertrophy and strength relationship

increased muscle size means increased muscle strength

atrophy and strength relationship

decreased muscle size means decreased muscle strength

sources of strength gains

altered neural control and increase muscle size

how can strength gain occur in neural adaptation?

cannot occur without plasticity but can without hypertrophy

what is strength a property of in addition to muscular strength?

motor system (neuromuscular junction)

elements of neural control

motor unit recruitment and stimulation frequency

how are motor units recruited?

normal: asynchronously

resistance training: synchronous

importance of synchronous recruitment

contributes to strength gain

how is strength gained with synchronous recruitment of motor units?

• facilitates contraction (↑ units firing at the same time)

• produces ↑ forceful contraction

• improve rate of force development

• improve capability to exert steady forces

what is motor unit rate coding?

frequency of motor units firing

what is a common trend in studies with the relationship of rate coding and resistance training?

limited suggests rate coding increases as resistance training increases

what movement does rate coding increase with?

rapid-movement and ballistic-type training

what is neural drive?

the activity of motor neurons

importance of neural drive in resistance training

increased motor units firing, improved motor unit synchronization, and increasing rate coding can lead to strength gains

mechanisms of muscle strength

neural control, motor unit recruitment, rate coding, neural drive, autogenic inhibition, hypertrophy, and satellite cells

autogenic inhibition

preventative mechanism for muscles exerting more force than the bones and tendons can tolerate

example of autogenic inhibition

golgi tendon organs inhibit mm. contraction if tendon tension is too high to prevent damage

what happens to autogenic inhibition during resistance training?

inhibitory impulses decrease by training which allows muscle to generate more force

other neural factors that contribute to muscle strength gain

structure of neuromuscular junction, increased endplate perimeter length, increased endplate area, and enhanced dispersion of acetylcholine receptors in the endplate region

types of muscle hypertrophy

transient and chronic

transient hypertrophy

temporary and is due to the edema formation from plasma fluid; gone within hours and does not increase strength

chronic hypertrophy

long term and is a structural change in muscle

what is chronic hypertrophy maximized by?

high-velocity eccentric training

importance of high-velocity eccentric training

disrupts sarcomere Z-lines (protein remodeling)

what can concentric-only training limit?

muscle hypertrophy and strength gains

what needs to happen for chronic muscle hypertrophy to be achieved?

the muscle needs to be trained to deliberate fatigue using high rep (low load) and low rep (high load) training

fiber hypertrophy

increases actin and myosin filaments while increasing sarcomere parallelity

importance of increasing sarcomere parallelity

increases protein synthesis

when does protein synthesis change in resistance training?

during: synthesis ↓ and degradation ↑

after: synthesis ↑ and degradation ↓

what is fiber hypertrophy facilitated by?

testosterone, growth hormones, and insulin-like growth factor 1 (all increased)

testosterone and fiber hypertrophy

natural anabolic steroid hormone

synthetic anabolic steroids

large increases in muscle mass and strength occur

acute and chronic levels of hormones during training

acutely increased but not required for anabolism and strength

anabolism

the combination of simple molecules to create complex molecules

fiber hypertrophy

most muscle hypertrophy is contributed to this

depends on resistance training intensity or load

what do higher intensities of training cause?

type II fiber hypertrophy

fiber hyperplasia

possible contributor to muscle hypertrophy under certain conditions (fiber splitting)

what do fiber hypertrophy and hyperplasia occur through?

satellite cells (myogenic stem cells)

how do satellite cells aid in fiber hypertrophy/hyperplasia?

skeletal muscle regeneration activated by stretch or injury

proliferate, migrate, and fuse

contributor of early strength gains

neural adaptation

effects of neural adaptation in early gains

substantial ↑ in 1 RM due to ↑ voluntary neural activation

when are neural factors most critical?

first 8-10 weeks

contributor of long term strength gains

fiber hypertrophy

effects of fiber hypertrophy in long-term gains

↑ in protein synthesis overall

when is hypertrophy a major factor?

after first 10 weeks

mechanisms of muscle strength loss

atrophy, inactivity, and immobilization

what happens with reduction of an activity?

major changes in muscle structure and function

when do major changes occur during immobilization?

after 6 hours: reduced protein synthesis which initiates the process of muscle atrophy

how much strength is lost in the first week of immobilization?

3-4% every day which decreases size and neuromuscular activity

reversible effects of atrophy on type I and type II fibers

cross sectional area decreases as cell content degenerates

what type fiber is affected more with immobilization?

type I because it decreases the % of these

`what type of fiber is affected more with cancer, diabetic sepsis, and congestive heart failure?

type II

why is detraining still important?

lost strength can be regained around 6 weeks and the 1 RM can match or exceed the previous one

example of detraining

prehab (muscle memory)

how do you maintain strength?

reduce training frequency

resistance training in children/adolescents

safe with proper safeguards because they can gain strength and mm. mass

7 year old introduction to resistance training

introduce child to basic exercises with little or no weight

8-10 year old introduction to resistance training

gradual increase in the number of exercises and load of each

11-13 year old introduction to resistance training

basic technique and progressive overloading then move into advanced exercise

14-15 year old introduction to resistance training

advanced youth programs with sport-specificity

16 year old introduction to resistance training

entry-level adult program

benefits strength training in older adults

helps restore age-related loss of muscle mass, improves quality of life and health, prevents falls, maintains bone density, and improves function

strength gains in older adults

dependent on neural adaptations with 25-50g of protein and decreased rates of protein synthesis