phenoytype, adaptive remodeling and metabolic drivers of resistance training adaptation.

Question 1

What is pennation angle?

Answer 1

The arrangement of fasicles

Question 2

Name the 4 type of pennation angle

Answer 2

• fusiform
• unipennate
• bipennate
• multipennate

Question 3

What are the two types of CSA?

Answer 3

1. anatomical - CSA runs perpendicular to the longitudinal axis of muscle itself
2. physiological - CSA runs perpendicular to the longitudinal axis of the fascicles

Question 4

Provide an overview of the muscle structure from macroscopic to ultrastructural level

Answer 4

Muscle –> fascicle –> myofiber –> myofibrils –> sarcomere

Question 5

Provide a study that investigates whole-muscle CSA and RT

Answer 5

Aoki et al 2009
- Rodent study investigating the effects of RT on whole muscle growth
- Results: increased muscle length ~20% of the soleus
- Results: increased no of sarcomeres ~27%

This is only evident in animals

Question 6

Provide study breaking down muscle growth as a whole

Answer 6

Roman et al, 1993
- 12-week RT on the elbow flexor
- Greatest increase in MPS is found in the belly of the muscle, not the distal ends ~23%
- Therefore muscle growth is not uniform

Question 7

Explain the geometric model of CSA

Answer 7

Length = increased length due to increase no of fascicles, therefore CSA
+11% length = +14% fascicles, therefore +30% CSA

Radius = increased pennation angle, therefore CSA
+14% length = +15% pennation angle, therefore 30% CSA

Question 8

Where defines the pennation angle?

Answer 8

• The point the fascicles emerge from the aponeurosis

Question 9

What are the 3 proposed/assumptions of muscle?

What is the most likely mechanism in humans?

Answer 9

1. Myofibril hypertrophy
2. Fibre splitting
3. Hyperplasia

Question 10

Evidence for myofibril hypertrophy

Answer 10

Aagard et al 2001
- 16 weeks RT
- Results: Increased quad CSA, T2 fibres and pennation angle

Question 11

Research into fibre splitting

Answer 11

Erikkson et al 2006
- steroid v no steroid use in powerlifters
- 3fold significant increase in fibre splitting in steroid users and without

Question 12

Research into hyperplasia

Answer 12

Tamaki et al 1992
- Squat RT in rodent increased number of fibres, compared to sprint training and no training
- only evident in animals

Question 13

Does sarcoplasmic hypertrophy contribute to overall muscle hypertrophy?

Answer 13

Dankel et al 2019 meta-analysis
- No evidence of disproportionate muscle swelling
- RT preserved T2 specific tension, therefore increased CSA is due to radial growth, not sarcoplasmic

Question 14

Provide further evidence against sarcoplasmic hypertrophy assumption

Answer 14

MacDougall et al 1982
- 6 months RT in normal healthy trained displayed higher levels of myofibrillar density compared to cytoplasmic density
- this is opposite in bodybuilders
- also an increase in T2 muscle fibre area dismisses assumption

Question 15

Describe how myofibers split

Answer 15

• New myofilaments grow around pre-existing myofibrils
• CSA reaches upper limit
• Myofibrils split into daughter myofibrils
• Cycle repeats

Question 16

Describe the 5 step process of satellite cells

Answer 16

1. Quiescent cell
2. Exercise activates quiescent cell
3. Quiescent proliferates, i.e. increase in number
4. Commit to function
5. Differentiate

Question 17

What are the two proteins that must be present to allow differentiation of quiescent satellite cell?

Answer 17

MRF4 and myogenin

Question 18

What are the acute and chronic roles of satellite cells?

Answer 18

Acute - repair of muscle tissue damage
Chronic - Maintain the myonuclear domain with hypertrophy, by increasing number of nucleuses, to support metabolic functions

Question 19

How is muscle mass regulated?

Answer 19

• Balance of MPS and MPB
• Enhanced by AA and exercise, via promoting synthesis

Question 20

How is protein made?

Answer 20

• Transcription: DNA in the nucleus is unzipped and exposes new mRNA sequence
• Translation: mRNA sequence leaves the cell to form AA chain and joined by peptides, consequently folded into new protein

Question 21

What are the three steps of translation?

Answer 21

1. Initiation: ribosome binds to mRNA sequence
2. Elongation: AA are transported and joined together and begin to form new peptide chain
3. Termination: ribosome is removed from mRNA sequence and new protein is formed

Question 22

Define mTOR and what complex of mTOR regulates what?

Answer 22

• Mammalian target of rapamycin
• mTORC1 regulates muscle growth

Question 23

Name 3 physiological stimuluses of mTOR, and 1 inhibitor

Answer 23

1. GF
2. AA
3. Energy
4. Stress or fasted state

Question 24

How does mTORC1 regulate

Answer 24

1. Physiological stimulus phosphorylates TSC2, becoming inactive, so increasing Rheb bound to GTP, therefore promoting MPS
2. Stressor activates TSC2, so Rheb is bound to GDP, therefore inhibiting MPS

Question 25

What stage of translation is the limiting factor?

Answer 25

Initiation. At rest nucleotides are stacked 80-100 nucleotides apart, compared to 27-30 apart during exercise Therefore initiation in translation is limiting factor in MPS

Question 26

Provide evidence of mTOR in translation

Answer 26

Chesley et al 1992 - RT increased MPS, to similar extent as the increase in RNA activity

Question 27

Evidence proving that mTORC1 is needed in MPS

Answer 27

Drummond et al 2009 - Rapamycin v placebo on mTORC1 - Rapamycin displayed blunted response in MPS, compared to 40% increase in MPS in placebo

Question 28

Name the two types of proposed mechanosensors and the proposed proteins they include

Answer 28

Lateral mechanosensor - Integrins and DGC Longitudinal - dystrophin, desmin, a-actinin

Question 29

Phosphatic acid as a proposed mechanosenosor

Answer 29

Neill et al 2009 - Animal study Used butanol to KO phosphatic acid vs control - Result: butanol attenuated mTORC1 response compared to control following eccentric RE

Question 30

Integrins as a mechanosensor?

Answer 30

Zou et al, 2011 - Overexpressed integrins in rodents - Greater mTORC1 response in overexpressed integrins rodent following acute exercise - Greater CSA growth in overexpressed integrins rodent following chronic exercise

Question 31

Is muscle fibre swelling a potential mechanosensor in humans

Answer 31

Farup et al 2015 - Muscle thickness following RT immediately increased, but returned to baseline 24hrs post-exercise Therefore not a mechanosensor - due to influx of cytosol fluid

Question 32

Is muscle fibre swelling a potential mechanosensor in animals

Answer 32

Low and Taylor 1998 - Swelling increased when placed in hypo-osmotic fluid, with significant uptake in glutamate - This was inhibited by cytoskeleton integrins Therefore limited evidence supporting in animals

Question 33

IS EIMD a stimulus for hypertrophy?

Answer 33

Moore et al 2015 - EIMD significant following 6 sets of EC, v EC - With significant increase in Z-band streaming and rates of MPS However, Nosaka et al 2001 - The repeated exposure to similar stimulus resulted in significant decrease in EIMD across 8 weeks - Therefore cannot be primary stimulus of hypertrophy

Question 34

Lactate as a stimulus

Answer 34

Moberg et al 2020 - Infused lactate or saline into participant during hard bouts of exercise - Significant increase in blood lactate and pH observed - NO change in rate of MPS Lactate is not a stimulus for MPS

Question 35

Alpha keto-gluterate as a stimulus

Answer 35

Cai et al 2016 - Added 2% AKG into drinking water - Observed a greater number of larger fibres in rodents Wax et al 2012 - L-arnine keto-gluterate supplemented to produce AKG, otherwise would be metabolised - no evidence of increasing 1RM - no research into the effect on muscle mass Supporting literature in animals and not in humans

Question 36

Describe the size principle

Answer 36

Muscle units are recruited from smallest to largest, typically T1 to T2 e.g. low mechanical load recruits small motor units, which increases with load and time under tension

Question 37

What happens in terms of type of muscle fibre with RT

Answer 37

Aagard et al 2001 - Overall 18% increase in total fibre area - T2 fibre increases by in area by 16% - NS in T1

Question 38

Evidence of manipulation of training variables

Answer 38

Fry et al 2014 - W + P greater number and size of T2 - B greater number and size of T1 Therefore manipulation of training variables underpin fibre size and strength

Question 39

What typically adapts first in response to RE

Answer 39

CNS

Question 40

Does hypertrophy occur earlier?

Answer 40

Brook et al 2015 - Single leg 6 week RT - MVC sig increase in trained leg - Evidence of crossover adaptations of untrained leg, but not increase in mass - MPS increased in weeks 0-3, not 3-6 This suggests that early changes in MPS may lead to hypertrophy

Question 41

Are early changes in MPS a stimulus for hypertrophy?

Answer 41

Damas et al 2016 - MPS increased early on, but so did Z-band streaming - therefore directed to muscle recovery and repair, not CSA

Question 42

Bigger the stronger?

Answer 42

Maugahan et al 1982 - Suggests yes Dankel et al 2016 - 1RM v 1RM + 3 sets 70%RM - 1RM + 3 sets = increase muscle size - Both groups displayed an increase in strength Therefore, not always the case Also links to CNS initial adaptations And the manipulation on training variables

Question 43

RT on different muscle groups

Answer 43

- RT of upper and lower limb - Greater increase in hypertrophy in upper - Maybe due to habitual loading of the legs, there becomes resistant OR different fibre composition OR training level

Question 44

Why may hypertrophy plateau?

Answer 44

Always et al, 1992 - no manipulation of variables - 24 week RT in b, bicep training - M had significant larger biceps - No increase in size or strength in M and F

Question 45

Is training status important in hypertrophy?

Answer 45

Tang et al, 2008 - Untrained = heightened MPS for greater duration ~16 hours, significantly shorter in trained Therefore, exposure to unaccustomed stimulus will prolong MPS

Question 46

Sex differences on hypertrophy

Answer 46

Abe et al 2000 - F displayed 60-80% size of strength compared to males - relative changes equal in M and F following 12 programme - therefore no influence of testosterone - menstrual cycle phase plays no role