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Locomotor & Exercise > Exercise Phys: Muscle, Fuels, & Fatigue > Flashcards

Exercise Phys: Muscle, Fuels, & Fatigue Flashcards

1
Q

How is percent body fat related to % type I muscle fibres?

A

more type I fibres = less body fat (more oxidative, tf burn fat)

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2
Q

How are mitochondria related to insulin sensitivity?

A

more mitochondria = more insulin sensitive; greater disposal rate of glucose in response to insulin

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3
Q

Acid pre-incubation staining for myosin-ATPase shows

A

Dark type I fibres; light type II fibres (because fast-twich fibres are acid-sensitive)

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4
Q

Alkaline pre-incubation staining for myosin-ATPase shows

A

Light type I fibres; dark type II fibres

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5
Q

Type I fibres

A

Slow oxidative, slow-twitch

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6
Q

Type IIa fibres

A

Fast oxidative glycolytic; fast-twitch

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7
Q

Type IIx fibres

A

Fast glycolitic; fatigable fast-twitch

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8
Q

Time to peak tension (ms)

A

I > IIa > IIx

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9
Q

Force/power output

A

IIx > IIa > I

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10
Q

Endurance capacity

A

I > IIa > IIx

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11
Q

Distribution in whole muscle

A

I > IIa > IIb

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12
Q

Mitochondrial density

A

I > IIa > IIb

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13
Q

Capillary density (cap/fibre)

A

I > IIa > IIb

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14
Q

Fibre area (um^2)

A

IIa > IIx > I

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15
Q

What is the order of fibre type recruitment?

A

ST, IIa, IIb at highest threshold; at maximum exercise all fibre types are activated to maximize force

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16
Q

% ST:FT in untrained

A

~50:50

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17
Q

T/F Type IIa fibres can be trained to be more oxidative (type I-like) even though their contractile properties remain fast

A

T

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18
Q

T/F ST fibres are easily trained to FT fibres

A

False; easier to train FT to become ST

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19
Q

Early and rapid increase in strength in response to strength training is attributable to

A

neuromuscluar adaptation - recruiting more muscle to generate more force

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20
Q

Muscle disuse leads to rapid loss of

A

protein and CSA

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21
Q

What is the muscle atrophy pathway?

A

Foxo (transcription factor) is normally inhibited by Akt pathway (mTOR, muscle growth) but is activated in bed rest leading to protein degradation and muscle atrophy

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22
Q

Increased muscle mass is stimulated via which pathways?

A

(GH) and IGF-1 acting via Pi3K insulin pathway to activate Akt (inh Foxo and tf atrophy) and mTOR; glucocorticoids also act via Akt

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23
Q

What are the mitochondrial adaptations in muscle in response to exercise training?

A

increased mitochondrial density and oxidative enzymes; reduced CHO use and lactate production; increased fat oxidation; enhanced endurance performance; improved insulin action

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24
Q

Blood lactate levels serve as a biomarker of

A

mitochondrial density

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25
Q

T/F ATP drives muscle contraction

A

True; myosin ATPase, Na/K-ATPase, Ca-ATPase (SERCA)

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26
Q

T/F We have significant stores of ATP in muscle

A

False; in exercise it must be regenerated via substrate level or oxidative phosphorlyation

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27
Q

Substrate-level phosphorylation involves

A

energy released from metabolic pathways and CP is transferred to rephosphorylate ADP to ATP

28
Q

Oxidative phosphorylation involves

A

e- reducing agents generated in TCA (NADH, FADH2) enter the ETC and regenerate ATP

29
Q

What happens to the rate of ATP generation as you move from CP and glycolysis (substrate-level) to CHO and fat oxidation (ox-phos)?

A

Rate of ATP generation decreases

30
Q

‘Hitting the wall’ refers to

A

being unable to maintain speed during endurance events because CHO stores are exhausted and metabolism is switching to fat oxidation - must slow down to maintain PO

31
Q

CP and glycolysis have _____ power and ________ capacity

A

high; low

32
Q

CHO and fat oxidation have _____ power and _____ capacity

A

low; high (depending on CHO reserves and diet)

33
Q

T/F Endurance athletes do not have enough body fat to sustain exercise

A

False; even the skinniest endurance athlete has more than enough fat to keep them going for many days

34
Q

What is the primary fuel in sprinting type activities?

A

anaerobic: ATP, PCr, glycolysis (glycogen –> lactate)

35
Q

What are the relative contributions of Pcr, ATP, and glycolysis in sprinting?

A

highest contribution by PCr initially which decreases over 10-30s; ATP smallest contributor and also decreases over time; glycolysis significant from 10s-30s

36
Q

What is the primary fuel in endurance exercise?

A

primarily aerobic (CHO and fat oxidation); 50% of 1 minute, 90% at 2 minutes; almost exclusively aerobic after 2 minutes

37
Q

Exercise becomes almost exclusively aerobic beyond

A

2 minutes

38
Q

T/F Protein cannot be used as a fuel in endurance exercise

A

False; muscle protein can be mobilized as fuel eg cyclist upper bodies

39
Q

Protein contributes ____ to total energy expenditure in endurance exercise in a well-fed individual

A

<5% once CHO is depleted

40
Q

The main fuels of aerobic metabolism are

A

CHO and fat

41
Q

As exercise intensity and energy expenditure increases, what happens with regards to CHO?

A

increased reliance on CHO (muscle glycogen)

42
Q

T/F At lower intensities, fat is making a major contribution as fuel

A

True; fat oxidation goes up at lower intensities, then goes down as intensity increases

43
Q

What is the ‘fat max’?

A

the intensity of exercise where you get maximal fat oxidation

44
Q

What are the relative contributions of muscle fats, plasma FFA, plasma glucose, and muscle glycogen during increasing intensity endurance exercise?

A

at rest predominantly plasma FFA and plasma glucose; muscle and plasma FFA use higher at lower intensities then decreases with increasing intensity; plasma glucose and muscle glycogen contributions increase with increasing intensity; muscle glycogen is the predominant fuel source at high intensity

45
Q

What is the predominant fuel at high intensity endurance exercise?

A

Muscle glycogen

46
Q

Over extensive time eg 4hrs endurance 65% VO2 max, what happens to reliance on CHO?

A

Reliance on CHO decreases as reliance on fat increases

47
Q

Endurance exercise ceases when

A

rate of CHO oxidation is insufficient to support exercise intensity - decreasing intensity then prolongs endurance exercise

48
Q

Ultra-distance runners typically operate at what %VO2 max?

A

50-60%

49
Q

What factors influence exercise metabolism and fuel selection?

A

exercise intensity and duration; diet; training; environmental temp; age; sex

50
Q

How does diet influence exercise metabolism?

A

high-CHO diet burns more CHO, high-fat burns more fat but intensity is limited

51
Q

How does training influence exercise metabolism?

A

training adaptations in muscle lead to reduced reliance on CHO as fuel - can go to a higher intensity on the same amt of CHO

52
Q

How does environmental temperature influence exercise metabolism?

A

exercise in heat = burn more CHO

53
Q

How does age influence exercise metabolism?

A

bc VO2 max declines with age, exercising at the same intensity is a higher relative intensity, tf burn more CHO

54
Q

How does sex influence exercise metabolism?

A

females use more fat than males, thought to be that oestrogen promotes fat oxidation

55
Q

Influences on exercise metabolism are mediated by

A

substrate availability, hormone levels (insulin, glucagon, catecholamines, GH, cortisol) and characteristics of skeletal muscle - with training, mitochondrial content increases and this alters substrate selection

56
Q

What is fatigue?

A

A reversible process which is induced by exercise and alleviated and reversed by rest - something has happened to change the characteristics of the muscle eg decrease in maximal force-generating capacity with prolonged exercise; Inability to maintain the required or expected force or PO - task-specific definition eg not being able to keep up with a competitor who is running at a faster pace

57
Q

What is muscle weakness?

A

Chronic reduction in force-generating capacity of the muscle

58
Q

Muscle weakness at rest indicates

A

problem with the muscle or NM system

59
Q

Muscle weakness induced by exercise eg premature fatigue indicates

A

CV (eg IHD) or metabolic defects

60
Q

What factors contribute to fatigue?

A

CNS central motor drive; muscle feedback - decreased ATP, increased H+ and ROS; lactic acid levels

61
Q

Removing muscle feedback to the brain eg fentanyl causes

A

increased exercise intensity and duration - brain is not getting feedback that would normally cause it to cease the muscle activity

62
Q

Blood lactate levels indicate

A

metabolic stress

63
Q

How is glycogen related to fatigue?

A

glycogen decreases more rapidly with increasing intensity in type I fibres; IMP (breakdown product of ADP) accumulates as glycogen declines; fatigue is thought to be an imbalance of ADP formation and ADP re-phos to ATP - running out of glycogen, can’t maintain ATP tf have to slow down

64
Q

T/F CHO ingestion prevents fatigue

A

False; ingestion (loading, CHO drinks during) can delay fatigue but does not prevent it

65
Q

How do you increase fatigue resistance?

A

training (physical, technical, mental); optimize nutrition (CHO, fluids, protein); heat acclimatization and cooling; drugs, supplements, gene doping eg PPARdelta to increase oxidative capacity

Locomotor & Exercise (11 decks)

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