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LAM 1 > Exercise Physiology > Flashcards

Exercise Physiology Flashcards

1
Q

What needs to happen for muscles to perform?

A

Adequate energy and oxygen supply to the muscles

Incorporates CVS, respiratory, locomotor, and endocrine systems as well as nutrition

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2
Q

What kind of races do thoroughbred and quarter horses run?

A

Thoroughbred- Marathon

Quarter- sprints

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3
Q

How best is athletic ability evaluated?

A

By VO2max (oxygen consumption)

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4
Q

What is the oxygen consumption of a fit racehorse?

A

160 mL/kg/min

2x that of elite humans and 2.6x cattle

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5
Q

Why do horses tend to have a higher hematocrit?

A

Splenic reserve volume allowing for rapid changes when necessary (prey animal)

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6
Q

How are the lungs adapted for exercise?

A

They’re really big

2x that of cattle with 1.6x the surface area for maximal gas exchange

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7
Q

What is the typical heart mass of a horse?

A

0.9-1% of BW in kg

Large compared to other athletic species
Secretariat was 2%

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8
Q

T/F: Max HR is similar to cattle but horses have greater CO and SV.

A

True

Normal rates are 25-44 and can get up to 220-250 at the end of a race

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9
Q

What percentage of body weight does a horse’s muscle mass comprise?

A

~50%

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10
Q

T/F: Horses have lower intramuscular glycogen stores than other animals.

A

False- they have higher ~140mmol/kg

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11
Q

T/F: Horses have higher number of mitochondria per unit of muscle weight.

A

True- approx 2x that of cattle

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12
Q

What are the three energy pathways for muscle?

A
  1. Creatine phosphate
  2. Anaerobic glycolysis
  3. Aerobic glycolysis and fat oxidation
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13
Q

What is the creatine phosphate pathway?

A

Generation of a ton of ATP that is only sustained for

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14
Q

How does anaerobic glycolysis work?

A

Glucose breakdown into lactate and ATP

Rapid process that produces enough energy to sustain for ~1min by itself before aerobic pathway kicks in

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15
Q

Why does anaerobic glycolysis occur?

A

In the cytoplasm

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16
Q

What is anaerobic glycolysis limited by?

A

The supply of glycogen in the muscle

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17
Q

When does the aerobic pathway become the primary pathway for energy creation?

A

After ~2min of exercise

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18
Q

Where does the aerobic pathway occur?

A

In the mitochondria

19
Q

How long does the aerobic pathway have to be running before it comes to maximal function?

A

35-40sec

20
Q

What is the aerobic pathway sustained by?

A

Continuous oxygen supply- as long as oxygen supply is adequate the aerobic pathway can be sustained for prolonged periods

21
Q

Where does the aerobic pathway get it’s fuel?

A

Circulating FFAs from adipose tissues and from muscle stores

22
Q

How much more ATP does the aerobic pathway created compared to the anaerobic pathway?

A

3x but the rate of production is slower

23
Q

Low-intensity exercise primarily uses what pathway?

A

Aerobic pathway

24
Q

At what percentage of glycogen depletion does the body switch to fat as an energy substrate?

A

20-30% depletion

25
Q

Why is it important to reserve glycogen stores in the horse?

A

Allows for some substrate to be saved so that you can switch from sub-maximal to high intensity exercise quickly

26
Q

At what percentage of VO2max is FFA oxidation the highest?

A

40-60%

27
Q

What can be used as a substrate at >60% CO2max?

A

Carbohydrates (glycogen)

28
Q

As exercise increases and oxygen consumption increases, what pathway may the horse revert back to? Why?

A

Anaerobic because they are no longer able to maintain the amount of oxygen required for the aerobic pathway to function adequately

29
Q

Why does training a sprinter for aerobic capacity help them even though they rarely enter the aerobic phase during competition?

A

May decrease lactic acid production

30
Q

What determines the proportion of energy derived from each substrate?

A
  • Speed/endurance of the work
  • Feed composition
  • Fitness level and conditioning
  • Muscle fiber composition
  • Age
31
Q

What is the substrate use summary?

A
  • Glucose plays a very small part in the energy produced (10%)
  • 60% of fat is used in low-intensity vs. 35% of fat used in high-intensity
  • 30% glycogen is used in low-intensity vs. 55% of glycogen used in high-intensity
32
Q

How many muscle fiber types are there?

A

3

33
Q

What are type I muscle fibers?

A

Slow twitch oxidative fibers

34
Q

What are some characteristics of type I muscle fibers?

A
  • Hydrolyze ATP slowly
  • High number of capillaries
  • Slow fatigue
  • Slow, repetitive movement
  • Poor power generation
35
Q

Where are type I muscle fibers mostly concentrated?

A

Stance sustaining muscles of the forelimbs

36
Q

What are type II muscle fibers?

A

Fast twitch fibers

Fast cross bridging cycle that generates force rapidly

37
Q

What are some characteristics of type IIA muscle fibers?

A
  • Large number of capillaries and mitochondria
  • Glycolytic and oxidative mechanisms
  • Sustain high power for prolonged periods
38
Q

What are some characteristics of type IIX muscle fibers?

A
  • 3x faster than IIA
  • Adapted for high power output  limited duration
  • Large cross-sectional area  low capillaries
39
Q

Where are type II muscle fibers mostly found?

A

Hind limbs

40
Q

What are type IIAX fibers?

A

Found in locotomor muscles

41
Q

What type of muscle fibers are used in postural muscles?

A

Type I

42
Q

What order are muscle fibers recruited in?

A

Type I > IIA > IIAX > IIX

43
Q

When are type IIAX mostly recruited?

A

Near maximal intensity or during extremely prolonged submaximal exercise

LAM 1 (10 decks)

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