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

Exercise Phys: Muscle, Fuels, & Fatigue Flashcards

(65 cards)

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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
T/F ATP drives muscle contraction
True; myosin ATPase, Na/K-ATPase, Ca-ATPase (SERCA)
26
T/F We have significant stores of ATP in muscle
False; in exercise it must be regenerated via substrate level or oxidative phosphorlyation
27
Substrate-level phosphorylation involves
energy released from metabolic pathways and CP is transferred to rephosphorylate ADP to ATP
28
Oxidative phosphorylation involves
e- reducing agents generated in TCA (NADH, FADH2) enter the ETC and regenerate ATP
29
What happens to the rate of ATP generation as you move from CP and glycolysis (substrate-level) to CHO and fat oxidation (ox-phos)?
Rate of ATP generation decreases
30
'Hitting the wall' refers to
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
CP and glycolysis have _____ power and ________ capacity
high; low
32
CHO and fat oxidation have _____ power and _____ capacity
low; high (depending on CHO reserves and diet)
33
T/F Endurance athletes do not have enough body fat to sustain exercise
False; even the skinniest endurance athlete has more than enough fat to keep them going for many days
34
What is the primary fuel in sprinting type activities?
anaerobic: ATP, PCr, glycolysis (glycogen --> lactate)
35
What are the relative contributions of Pcr, ATP, and glycolysis in sprinting?
highest contribution by PCr initially which decreases over 10-30s; ATP smallest contributor and also decreases over time; glycolysis significant from 10s-30s
36
What is the primary fuel in endurance exercise?
primarily aerobic (CHO and fat oxidation); 50% of 1 minute, 90% at 2 minutes; almost exclusively aerobic after 2 minutes
37
Exercise becomes almost exclusively aerobic beyond
2 minutes
38
T/F Protein cannot be used as a fuel in endurance exercise
False; muscle protein can be mobilized as fuel eg cyclist upper bodies
39
Protein contributes ____ to total energy expenditure in endurance exercise in a well-fed individual
<5% once CHO is depleted
40
The main fuels of aerobic metabolism are
CHO and fat
41
As exercise intensity and energy expenditure increases, what happens with regards to CHO?
increased reliance on CHO (muscle glycogen)
42
T/F At lower intensities, fat is making a major contribution as fuel
True; fat oxidation goes up at lower intensities, then goes down as intensity increases
43
What is the 'fat max'?
the intensity of exercise where you get maximal fat oxidation
44
What are the relative contributions of muscle fats, plasma FFA, plasma glucose, and muscle glycogen during increasing intensity endurance exercise?
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
What is the predominant fuel at high intensity endurance exercise?
Muscle glycogen
46
Over extensive time eg 4hrs endurance 65% VO2 max, what happens to reliance on CHO?
Reliance on CHO decreases as reliance on fat increases
47
Endurance exercise ceases when
rate of CHO oxidation is insufficient to support exercise intensity - decreasing intensity then prolongs endurance exercise
48
Ultra-distance runners typically operate at what %VO2 max?
50-60%
49
What factors influence exercise metabolism and fuel selection?
exercise intensity and duration; diet; training; environmental temp; age; sex
50
How does diet influence exercise metabolism?
high-CHO diet burns more CHO, high-fat burns more fat but intensity is limited
51
How does training influence exercise metabolism?
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
How does environmental temperature influence exercise metabolism?
exercise in heat = burn more CHO
53
How does age influence exercise metabolism?
bc VO2 max declines with age, exercising at the same intensity is a higher relative intensity, tf burn more CHO
54
How does sex influence exercise metabolism?
females use more fat than males, thought to be that oestrogen promotes fat oxidation
55
Influences on exercise metabolism are mediated by
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
What is fatigue?
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
What is muscle weakness?
Chronic reduction in force-generating capacity of the muscle
58
Muscle weakness at rest indicates
problem with the muscle or NM system
59
Muscle weakness induced by exercise eg premature fatigue indicates
CV (eg IHD) or metabolic defects
60
What factors contribute to fatigue?
CNS central motor drive; muscle feedback - decreased ATP, increased H+ and ROS; lactic acid levels
61
Removing muscle feedback to the brain eg fentanyl causes
increased exercise intensity and duration - brain is not getting feedback that would normally cause it to cease the muscle activity
62
Blood lactate levels indicate
metabolic stress
63
How is glycogen related to fatigue?
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
T/F CHO ingestion prevents fatigue
False; ingestion (loading, CHO drinks during) can delay fatigue but does not prevent it
65
How do you increase fatigue resistance?
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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