Week 9 - The effects of Resistance training

Question 1

Muscular strength

Answer 1

maximal force that a muscle group can generate (1RM)

Question 2

Muscular endurance

Answer 2

ability to make repeated contractions against a submaximal load

Question 3

What does high-resistance training (6-10 reps till fatigue) result in?

Answer 3

strength increases

Question 4

What does low-resistance training (35-40reps till fatigue) result in?

Answer 4

endurance increases

Question 5

What does ageing result in?

Answer 5

• the loss of both muscle mass (termed sarcopenia) and strength
• atrophy type two fibers
• reduced number of both type I and II fibers (loss of motor neurons)

Question 6

How does resistance training increase muscle strength?

Answer 6

by changes in both the nervous system and muscle fiber size/function

Neural adaptations are responsible for early gains in strength (first 8 weeks).
- This is supported by the fact that muscular strength increases in first two weeks of training without increases in muscle fiber size.

Adaptations within muscle fibers occur later. For example, increase in muscle fiber specific tension and increased muscle mass.

Question 7

What are the neural adaptations that result in early gains in muscle strength?

Answer 7

• Increased neural drive
• Increase number of motor units recruited
• Increased firing rate of motor units
• Increased motor unit synchronization
• Improved neural transmission across neuromuscular junction
• Increased size of NmJ and vesicles containing ACh

Question 8

Summarise the 4 resistance training-induced physiological adaptations.

Answer 8

1) NS: Increased neural drive + possible changes in ratio of agonist/antagonist activation which occurs rapidly after training (2-8 weeks).

2) Increased muscle fiber force production, specifically in type I fibers due to an increased calcium sensitivity which results in a greater number of cross-bridges bound to actin.

3) Hypertrophy (specifically in type II fibers) which increases muscle mass.

4) Muscle fiber type shift from type IIx to IIa fibres.

Question 9

What is the dominant factor in resistance training-induced increases in muscle mass?

Answer 9

Hypertrophy - incr. cross-sectional area of muscle fibres

Question 10

What is hypertrophy due to?

Answer 10

increased muscle proteins - actin and myosin

Question 11

What transition occurs in fiber type due to resistance training?

Answer 11

type IIx to type IIa

Question 12

What is the difference between hyperplasia and hypertrophy?

Answer 12

Hyperplasia is the increased number of fibers whereas hypertrophy is the increased cross-sectional area of muscle fibers.

Question 13

Muscle growth occurs because protein synthesis exceeds rate of breakdown. But how long must synthesis exceed breakdown to achieve significant fibre growth?

Answer 13

3 or more weeks

Question 14

What % increase in muscle protein synthesis do we see with 1-4 hours post-exercise?

Answer 14

50-150%

This increase in muscle protein synthesis is elevated up to 30 to 48h after training depending on training status.

Question 15

What are the key factors that contribute to resistance training-induced increases in muscle protein synthesis?

Answer 15

• mRNA increases resulting in protein synthesis at the ribosome.
• Ribosomes increase in number and elevate muscle’s protein synthesis capacity.
• Activation of the protein kinase mTOR is THE KEY FACTOR accelerating protein synthesis following a bout of resistance training.

Question 16

What are the two signaling molecules that stimulate mTOR activation? How does resistance training influence these signaling molecules?

Answer 16

Phosphatidic acid (PA) and Ras homolog enriched in brain (Rheb)

Question 17

What is the time course of molecular responses to resistance training? Seconds - Minutes - Hours

Answer 17

Increased Rheb and PA = seconds

Increased mTOR activation = minutes

Increased protein synthesis = hours

Question 18

What other factors are linked to resistance training-induced hypertrophy?

Answer 18

Insulin-like growth factor-1 (IGF-1) and growth hormone.

• Small increases after a single bout of resistance training.
• Linked to mTOR activation and have a potential to increase muscle protein synthesis.

Question 19

Role of satellite cells in resistance training-induced hypertrophy.

Answer 19

Resistance training activates satellite cells to divide and fuse with adjacent muscle fibers to increase myonuclei.

The addition of new myonuclei is required to support increased protein synthesis in larger muscle fibers which is essential to achieve maximal hypertrophy.

Question 20

What % of the differences in muscle mass between individuals is due to genetic variation?

Answer 20

80%

Question 21

How can differences in the magnitude of RT induced hypertrophy be explained?

Answer 21

Due to variations in individuals’ ability to activate specific protein synthesis genes in skeletal muscle in response to RT.

Question 22

What does the cessation of RT result in?

Answer 22

muscle atrophy and a loss of strength

Question 23

Compared to endurance training, is the rate of detraining following resistance training faster or slower?

Answer 23

Slower

Question 24

Does the recovery of strength loss with retraining occur slow or fast?

Answer 24

Fast - within 6 weeks

Question 25

What is the ability for a rapid recovery of training losses called?

Answer 25

muscle memory

Question 26

How can we explain muscle memory - rapid recovery?

Answer 26

This can be explained by the resistance training-induced increase in myonuclei in the trained fibers that are not lost during detraining.

Question 27

What does prolonged skeletal muscle inactivity lead to?

Answer 27

Rapid fiber atrophy

• 20-30days of muscle inactivity can result in 20-30% reduction in muscle fiber size.

Question 28

What is the conservation of muscle mass dependent upon?

Answer 28

the balance between protein synthesis and rates of protein degradation

Question 29

What is the key mechanism responsible for inactivity-induced muscle atrophy?

Answer 29

Increased radical production - it promotes muscle atrophy during prolonged inactivity by depressing protein synthesis and increasing degradation.

Question 30

What issues may there be with strength training and endurance training together?

Answer 30

it impairs strength gains compared to strength training alone

Question 31

What are the potential mechanisms for the combination of endurance training with strength training impairing strength gains?

Answer 31

• Neural factors: impaired motor unit recruitment
• Overtraining

Main mechanism = Depressed protein synthesis. ET cell signaling can interfere with protein synthesis via inhibition of mTOR by the activation of AMPK.

Question 32

A single bout of resistance exercise training increases muscle protein synthesis by as much as ______% above resting levels?

Answer 32

50-150%

Question 33

What is the major regulator of protein synthesis and muscle size?

Answer 33

mTOR