The Mechanisms of Muscle Hypertrophy and their Application to Resistance Training

Question 1

What is hyperplasia?

Answer 1

Results in an increased number of fibres within a muscle

Question 2

What happens when skeletal muscle is subjected to an overload stimulus?

Answer 2

Causes change in myofibers and related extracellular matrix. This sets of chain of myogenic events which lead to increase in size and number of actin and myosin and total number of sarcomeres in parallel.

Question 3

How do satellite cells mediate hypertrophy?

Answer 3

Usually dormant but come active when enough mechanical stimulus is imposed on skeletal muscle. Once aroused, satellite cells increase rapidly in number and fuse to existing cells to create new myofibers, providing precursors needed for repair and subsequent growth of new muscle tissue.

Question 4

How do satellite cells facilitate muscle hypertrophy?

Answer 4

Donate extra nuclei to muscle fibres, increasing capacity to synthesize new proteins.

Question 5

Exercise-induced muscle hypertrophy is facilitated by a number of signalling pathways, what are they?

Answer 5

• mTOR
• MAPK
• CA2+ dependent pathways

Question 6

How does the Akt/mTOR pathway work?

Answer 6

Acts as master network regulating skeletal muscle growth. When activated, Akt signals mTOR, which exerts effects on various downstream targets promoting hypertrophy in muscle tissue.

Question 7

How does the MAPK pathway work?

Answer 7

Master regulator of gene expression, redox status, and metabolism. Specific to exercise-induced skeletal muscle hypertrophy, MAPK links cellular stress with an adaptive response in myocytes.

Question 8

What does elevated anabolic hormone concentration increase the likelihood of?

Answer 8

Receptor interactions, facilitating protein metabolism and muscle growth.

Question 9

What are the 3 most widely studied hormones?

Answer 9

• Insulin-like GF
• Testosterone
• Growth Hormone

Question 10

What is the role of IGF-1?

Answer 10

Thought to provide main anabolic response for the body as a whole and shows enhanced effects in response to mechanical loading.

Question 11

What is availability of IGF-1 controlled by?

Answer 11

IGF-1 binding proteins - these either stimulate or inhibit effects of IGF-1 after binding to a specific IGFBF.

Question 12

IGF-1 activates L-type calcium channel gene expression causing…?

Answer 12

An increased intracellular Ca2+ concentration. This leads to activation of multiples anabolic Ca2+ dependent pathways .

Question 13

As well as muscle tissue, what else does testosterone interact with?

Answer 13

Neuron receptors, thus increasing number of neurotransmitters released.

Question 14

What does testosterone bind to in the blood?

Answer 14

Albumin (38%), steroid hormone binding globulin (60%), circulating in the blood (2%)

Question 15

How does testosterone reach the chromosomal DNA inside a cell?

Answer 15

Unbound testosterone binds to androgen receptors of target tissues (located in cytoplasm). Causes a conformational change which transports testosterone to cell nucleus.

Question 16

What does testosterone do to satellite cells?

Answer 16

Promotes satellite cell replication and activation, resulting in an increase in number of myogenically committed satellite cells.

Question 17

What does resistance training do to androgen receptor content in humans?

Answer 17

Upregulates it.

Question 18

What does Growth Hormone do?

Answer 18

Acts as a repartitioning (dividing) agent to induce fat metabolism towards mobilization of TG and stimulate cellular uptake and incorporation of amino acids into various proteins, like muscle.

Question 19

What secretes GH?

Answer 19

Anterior pituitary gland.

Greatest nonexercised secretions during sleep.

Question 20

What type of exercise maximises cell swelling?

Answer 20

Exercise which relies heavily on glycolysis. The resultant lactate accumulation acts as primary contributor to osmotic changes in skeletal muscle.

Question 21

What 3 primary factors are responsible for initiating hypertrophic response to resistance exercise?

Answer 21

• Mechanical tension
• Muscle damage
• Metabolic stress

Question 22

Load <?% 1RM is considered insufficient to promote substantial hypertrophy/

Answer 22

65%

Question 23

Why are high reps inferior to moderate/low reps in eliciting hypertrophy?

Answer 23

Load is inadequate to recruit and fatigue highest threshold motor units.

Question 24

What systems are low AND moderate reps reliant on?

Answer 24

• Low = PC system
• Moderate = anaerobic glycolysis.

Question 25

How would you get a ‘pump’?

Answer 25

Veins taking blood out of working muscle are compressed while arteries continue to deliver blood, creating an increased concentration of intramuscular blood plasma. This causes plasma to seep out of capillaries into interstitial spaces, build up of this fluid causes extracellular pressure gradient, causing flow of plasma back into muscle causing a ’pump’.

Question 26

(?) Volume programs mediate GH release

Answer 26

High

Question 27

What is ‘overreaching’? (in terms of volume)

Answer 27

Planned, short-term increase in volume/intensity intended to improve performance.

Question 28

Is overtraining due more to volume or intensity?

Answer 28

Volume.

Question 29

Why is frequent exercise rotation needed to fully maximise hypertrophic response?

Answer 29

To stimulate all fibres, varying exercise parameters cause different activation patterns within muscle compartments.

Question 30

Why are short rest intervals used?

Answer 30

To generate metabolic stress, heighten anabolic processes associated with metabolite build up.

Question 31

Why are long rest intervals used?

Answer 31

Afford full recovery of strength between sets.

Question 32

Why are moderate rest intervals a good compromise?

Answer 32

Most strength is regained within 1 min of set completion. Traning with shorter rest = adaptations allowing lifter to sustain higher % 1RM during training.

Question 33

What is a positive AND a negative about training til failure?

Answer 33

P = TTF hypothesized to activate more MUs
N = TTF may increase potential for overtraining.

Question 34

To increase hypertrophy, should concentric reps be fast or slow?

Answer 34

Fast (some argue moderate speed)

Question 35

Should eccentric component of rep be fast or slow?

Answer 35

Slow