Exercise Physiology: Muscle, Fuels and Fatigue Flashcards
What fuels do type I muscle fibres rely heavily on?
Oxidative fuels, including lipids
What is the association between type I fibres and lipid storage?
If you have more type I fibres, you store less lipid
What proportion of body mass is made of muscle in most people?
40%
Which muscle fibre types are mainly found in humans?
Type I and IIa
Which muscle fibre types are probably found only in super sprinters, who are most likely born with them?
Type IIx
What is another name for type I fibres?
Slow twitch fibres
What is another name for type IIa fibres?
Fast twitch fibres
Which muscle fibre type reaches peak tension first?
Type IIa
Rank the muscle fibre types in order of force/power output, from highest to lowest
Type IIx >IIa >I
Rank the muscle fibre types in order of endurance capacity, from highest to lowest
Type I >IIa >IIx
Rank the muscle fibre types in order of proportion in whole muscle, from highest to lowest
Type I >IIa >IIx
Rank the muscle fibre types in order of mitochondrial density, from highest to lowest?
Type I >IIa >IIx
How do type I fibres in females differ from those in males, and why?
Females have slightly more type I fibres and have more efficient oxidation
Thought to be because of oestrogen
As the muscular force generated increases, in which order are muscle fibre types recruited?
Recruit slow twitch, smaller fibres first
Fast twitch fibres recruited next
Can muscle fibre types be changed?
Can turn some fast twitch fibres, especially type IIa, into slow twitch fibres
No real evidence to show switch from slow twitch fibres to fast twitch
In response to high-intensity resistance training, what is the rate of neural and muscle adaptations?
Neural adaptations happen very quickly, but muscle adaptation much slower
What is the relationship between muscle mass and disuse?
Muscle mass lost very quickly with inactivity
What does bed rest activate in muscles?
Atrophy proteins via unknown mechanism
What are the mitchochondrial adaptations to exercise training?
Increased mitochondrial density and oxidative enzymes
Reduced carbohydrate use and lactate production
Increased fat oxidation
Enhanced endurance performance
Improved insulin action
What is the relationship between exercise and skeletal muscle GLUT4 expression?
Exercise activates GLUT4 expression in muscles, independent of insulin
How long do ATP stores in muscle last for during exercise?
2-15 sec
What can creatine phosphate do during explosive activity?
Transfer its phosphate to ADP
What happens to the rate of exercise when using lipids as an energy source, and why?
Becomes slower
Rate of ATP production significantly slower when using free fatty acids compared to carbohydrates
Is the amount of ATP that can be generated from free fatty acid oxidation limited?
No, not even in very skinny marathon runner
What is the relative use of fuels during different duration sprints?
Power output decreases with increasing duration
Amount of glycolysis doesn’t really change
Energy from phosphocreatine makes significant contribution, which decreases with time
What is the relative use of fuels during different intensities of exercise?
As exercise intensity increases, glycogen becomes most important fuel source
Fat usage increases with intensity, then decreases, until it will eventually stop
What are some factors influencing exercise metabolism?
Exercise intensity and duration Diet Training Environmental temperature Age and gender
How does training influence fat utilisation?
With training, increase fat utilisation for given exercise intensity
How does the environmental temperature influence fuel usage during exercise?
Increased temperature > increased carbohydrate use
What is fatigue?
Reduction in force and power generating capacity
What is fatigue induced by?
Muscle contractile activity
Is fatigue reversible?
Yes
What is weakness induced by?
Happens at rest, and would probably be exacerbated by muscle contractile activity
As you undertake a required force, your maximum possible force decreases. When does this become a problem?
Maximum possible force becomes less than required force
What happens when muscle glycogen stores are depleted during exercise?
Unable to maintain exercise intensity
What effect does carbohydrate ingestion before exercise have on your exercise capacity?
Improves it
