Exercise Physiology

Question 1

What needs to happen for muscles to perform?

Answer 1

Adequate energy and oxygen supply to the muscles

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

Question 2

What kind of races do thoroughbred and quarter horses run?

Answer 2

Thoroughbred- Marathon

Quarter- sprints

Question 3

How best is athletic ability evaluated?

Answer 3

By VO2max (oxygen consumption)

Question 4

What is the oxygen consumption of a fit racehorse?

Answer 4

160 mL/kg/min

2x that of elite humans and 2.6x cattle

Question 5

Why do horses tend to have a higher hematocrit?

Answer 5

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

Question 6

How are the lungs adapted for exercise?

Answer 6

They’re really big

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

Question 7

What is the typical heart mass of a horse?

Answer 7

0.9-1% of BW in kg

Large compared to other athletic species
Secretariat was 2%

Question 8

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

Answer 8

True

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

Question 9

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

Answer 9

~50%

Question 10

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

Answer 10

False- they have higher ~140mmol/kg

Question 11

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

Answer 11

True- approx 2x that of cattle

Question 12

What are the three energy pathways for muscle?

Answer 12

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

Question 13

What is the creatine phosphate pathway?

Answer 13

Generation of a ton of ATP that is only sustained for

Question 14

How does anaerobic glycolysis work?

Answer 14

Glucose breakdown into lactate and ATP

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

Question 15

Why does anaerobic glycolysis occur?

Answer 15

In the cytoplasm

Question 16

What is anaerobic glycolysis limited by?

Answer 16

The supply of glycogen in the muscle

Question 17

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

Answer 17

After ~2min of exercise

Question 18

Where does the aerobic pathway occur?

Answer 18

In the mitochondria

Question 19

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

Answer 19

35-40sec

Question 20

What is the aerobic pathway sustained by?

Answer 20

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

Question 21

Where does the aerobic pathway get it’s fuel?

Answer 21

Circulating FFAs from adipose tissues and from muscle stores

Question 22

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

Answer 22

3x but the rate of production is slower

Question 23

Low-intensity exercise primarily uses what pathway?

Answer 23

Aerobic pathway

Question 24

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

Answer 24

20-30% depletion

Question 25

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

Answer 25

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

Question 26

At what percentage of VO2max is FFA oxidation the highest?

Answer 26

40-60%

Question 27

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

Answer 27

Carbohydrates (glycogen)

Question 28

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

Answer 28

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

Question 29

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

Answer 29

May decrease lactic acid production

Question 30

What determines the proportion of energy derived from each substrate?

Answer 30

- Speed/endurance of the work - Feed composition - Fitness level and conditioning - Muscle fiber composition - Age

Question 31

What is the substrate use summary?

Answer 31

* 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

Question 32

How many muscle fiber types are there?

Answer 32

3

Question 33

What are type I muscle fibers?

Answer 33

Slow twitch oxidative fibers

Question 34

What are some characteristics of type I muscle fibers?

Answer 34

- Hydrolyze ATP slowly - High number of capillaries - Slow fatigue - Slow, repetitive movement - Poor power generation

Question 35

Where are type I muscle fibers mostly concentrated?

Answer 35

Stance sustaining muscles of the forelimbs

Question 36

What are type II muscle fibers?

Answer 36

Fast twitch fibers Fast cross bridging cycle that generates force rapidly

Question 37

What are some characteristics of type IIA muscle fibers?

Answer 37

* Large number of capillaries and mitochondria * Glycolytic and oxidative mechanisms * Sustain high power for prolonged periods

Question 38

What are some characteristics of type IIX muscle fibers?

Answer 38

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

Question 39

Where are type II muscle fibers mostly found?

Answer 39

Hind limbs

Question 40

What are type IIAX fibers?

Answer 40

Found in locotomor muscles

Question 41

What type of muscle fibers are used in postural muscles?

Answer 41

Type I

Question 42

What order are muscle fibers recruited in?

Answer 42

Type I > IIA > IIAX > IIX

Question 43

When are type IIAX mostly recruited?

Answer 43

Near maximal intensity or during extremely prolonged submaximal exercise