Week 9 - The effects of Resistance training Flashcards

1
Q

Muscular strength

A

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

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2
Q

Muscular endurance

A

ability to make repeated contractions against a submaximal load

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3
Q

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

A

strength increases

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4
Q

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

A

endurance increases

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5
Q

What does ageing result in?

A
  • 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)
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6
Q

How does resistance training increase muscle strength?

A

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.

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7
Q

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

A
  • 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
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8
Q

Summarise the 4 resistance training-induced physiological adaptations.

A

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.

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9
Q

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

A

Hypertrophy - incr. cross-sectional area of muscle fibres

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10
Q

What is hypertrophy due to?

A

increased muscle proteins - actin and myosin

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11
Q

What transition occurs in fiber type due to resistance training?

A

type IIx to type IIa

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12
Q

What is the difference between hyperplasia and hypertrophy?

A

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

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13
Q

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

A

3 or more weeks

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14
Q

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

A

50-150%

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

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15
Q

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

A
  • 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.
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16
Q

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

A

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

17
Q

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

A

Increased Rheb and PA = seconds

Increased mTOR activation = minutes

Increased protein synthesis = hours

18
Q

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

A

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.
19
Q

Role of satellite cells in resistance training-induced hypertrophy.

A

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.

20
Q

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

A

80%

21
Q

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

A

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

22
Q

What does the cessation of RT result in?

A

muscle atrophy and a loss of strength

23
Q

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

A

Slower

24
Q

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

A

Fast - within 6 weeks

25
Q

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

A

muscle memory

26
Q

How can we explain muscle memory - rapid recovery?

A

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

27
Q

What does prolonged skeletal muscle inactivity lead to?

A

Rapid fiber atrophy

  • 20-30days of muscle inactivity can result in 20-30% reduction in muscle fiber size.
28
Q

What is the conservation of muscle mass dependent upon?

A

the balance between protein synthesis and rates of protein degradation

29
Q

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

A

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

30
Q

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

A

it impairs strength gains compared to strength training alone

31
Q

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

A
  • 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.

32
Q

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

A

50-150%

33
Q

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

A

mTOR