Studied by 7 people
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
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