Exercise Physiology Flashcards
1
Q
Exercise requires what 2 things?
A
- Energy supply for the muscles
- Oxygen delivery to this tissues
2
Q
Thoroughbreds typically race what distance range?
At what speed?
A
- Distance: 800-5000 meters
- 64 km/hr, 40 mph
3
Q
Quarter horses typically race at what distance?
At what speed?
A
- Distance:
4
Q
What is the maximum oxygen consumption level seen with fit racehorses?
How much greater is this compared to cattle?
A
- 160 ml/kg/min
- 2.6 times that of cattle
5
Q
How does HR, CO and SV compare between a fit racehorse and cattle?
A
- HR similar to cattle
- CO and SV greater in horses
6
Q
Are muscle mass and lung field generally larger in a horse or cattle?
A
Horse
7
Q
How much larger are the lungs of a horse compared to cattle?
Surface area?
A
- Lungs 2X size of cattle
- 1.6 times greater surface area
8
Q
The heart mass of a horse is typically what percentage of their body weight?
A
0.9-1% of body weight
9
Q
Muscle mass in horses is what percentage of body weight?
A
50% of body weight
10
Q
Do horses have a higher or lower concentration of intramuscular glycogen compared to other species?
What is the amount?
A
- Higher concentration
- 140 mmol/kg of muscle
11
Q
How much greater is the ratio of mitochondria per unit of muscle weight in horses compared to cattle?
A
2 times greater in horses
12
Q
The combination of what 2 factors make horses good at aerobic exercise?
A
- Higher concentration of intramuscular glycogen
- Larger number of mitochondria per unit of muscle weight
13
Q
What are 2 different storage forms from which energy can be utilized?
A
- Intramuscular glycogen and triglycerides
- Extra-muscular stores such as adipose tissue and liver glycogen
14
Q
What are 3 forms of readily usable energy?
A
- ATP
- Phosphocreatine Pathway
- ADP-myokinase
15
Q
Which energy pathway can create a tremendous amount of ATP in a fraction of a second?
A
Phosphocreatine pathway
16
Q
Which energy pathway is only utilized during the initial seconds of exercise?
A
Phosphocreatine pathway
17
Q
Which energy pathway allows other pathways to come up to speed?
A
Phosphocreatine pathway
18
Q
With the anaerobic pathway, how much ATP is produced?
How quickly?
A
- Small amount of ATP
- Very rapid production of energy
19
Q
With the anaerobic pathway, what is produced from pyruvate?
Where does this take place?
A
- Lactic acid
- In cytoplasm
20
Q
With the aerobic pathway, what is produced from pyruvate?
Where does this take place?
A
- Acetyl CoA
- In mitochondria
21
Q
What does the aerobic pathway depend on?
A
Depends on continuous O2 supply.
22
Q
Which pathway generates more ATP, aerobic or anaerobic?
A
Aerobic
23
Q
What is an example of an aerobic pathway?
A
Beta oxidation of free fatty acids
24
Q
Beta oxidation of free fatty acids produces how much more ATP?
A
3x more
25
Which aerobic pathway requires more oxygen?
| Is the rate of energy production with this pathway fast or slow?
- Beta oxidation of free fatty acids
| - Rate of energy production slow
26
Is low intensity exercise largely aerobic or anaerobic?
Largely aerobic
27
At what point with low intensity exercise will the energy source move to fat as a substrate?
At 20-30% glycogen depletion
28
Free fatty acid oxidation is highest at what percentage VO2 max?
40-60%
29
What happens as intensity of exercise increases?
Additional work above this engenders oxidation of carbohydrates.
30
If intensity is increased but still within limits of the aerobic pathway, what happens?
Glucose from circulation is used and glycogen from intramuscular stores are mobilized.
31
With an increase in intensity come an increase in what?
Increase in oxygen demand and delivery.
32
What happens with a further increase in intensity?
| What does this lead to?
- ATP needs are not met by oxygen delivery
| - Anaerobic pathway
33
What are 5 factors that the proportion of energy derived from each storage form are dependent on?
- Speed
- Feed
- fitness
- Muscle fiber composition
- Age of the horse
34
At 30% exercise intensity (VO2 max), what percentage of energy expenditure comes from glucose?
Fat?
Glycogen?
- 10%
- 60%
- 30%
35
At 60% intensity (VO2 max), what percentage of energy expenditure comes from glucose?
Fat?
Glycogen?
- 10%
- 35%
- 55%
36
How are muscle fiber types differentiated?
Differentiated by myosin heavy chain isoforms.
37
What are the 3 pure forms (contain a single isoform) of muscle fibers seen in horses?
- Type I
- Type IIA
- Type IIX
38
What are the 2 hybrid forms of muscle fibers seen in horses?
- Type I and IIA
| - Type IIAX
39
What type of fibers are slow twitch oxidative fibers?
Type I fibers
40
How quickly do Type I fibers hydrolyze ATP?
Hydrolyze ATP slowly
41
Which type of fibers have a high number of capillaries and a high oxidative capacity?
Type I fibers
42
Do Type 1 fibers fatigue quickly or slowly?
Fatigue slowly
43
What type of movement are Type I fibers responsible for?
Slow repetitive movement
44
What do Type I fibers sustain?
| What are they poor at?
- Sustain isometric force
| - Poor at power generation
45
Do Type I fibers form small or large bundles?
Small bundles
46
What type of fibers are fast twitch?
Type II fibers
47
What type of fibers show fast cross-bridging cycles?
Type II fibers
48
Do Type II fibers generate force slowly or rapidly?
Generate force rapidly
49
What type of fibers are fast oxidative glycolytic (FOG) fibers?
Type IIA fibers
50
What type of fibers have large numbers of capillaries and mitochondria?
Type IIA fibers
51
Which type of fibers utilize glycolytic and oxidative mechanisms?
Type IIA fibers
52
How long can Type IIA fibers sustain high power?
For prolonged periods
53
What type of fibers are fast glycolytic fibers (FG)?
Type IIX fibers
54
How much faster are Type IIX fibers compared to Type IIA fibers?
3x faster than Type IIA fibers
55
Do Type IIX fibers form small or large bundles?
Large bundles
56
What are Type IIX fibers adapted for?
Adapted for high power output with limited duration.
57
Do Type IIX fibers have a high or low number of capillaries?
Low number of capillaries
58
Type IIAX fibers are intermediate between what other 2 fiber types?
- Type IIA fibers
| - Type IIX fibers
59
The forelimb is mainly composed of what type of muscle fibers?
Type I fibers
60
Since the hindlimbs are the main source of propulsion, they have a high proportion of what muscle type?
Type II fibers
61
Posture maintenance is controlled by what type of fibers?
Type I fibers
62
In what order are muscle fibers recruited?
- Type I fibers
- Type IIA fibers
- Type IIAX fibers
- Type IIX fibers
63
Type IIX fibers are only recruited when?
Recruited near maximal intensity (sprinting and jumping) and during extremely prolonged submaximal exercise.
64
What are 4 factors on which the relative contribution of each pathway depends on?
- Nature, intensity and duration of activity
- Muscle fiber type composition
- Available O2
- Substrate composition
65
Splenic contractions can cause hematocrits to rise to what percentage?
60-70%
66
Splenic contraction can increase oxygen delivery in what 2 ways?
- Increase hemoglobin
| - Increase oxygen carrying capacity of the blood
67
The cardiac output in a resting horse is what?
| This can increase to what?
- 25 L/min
| - 300 L/min
68
What is normal heart rate in a horse?
| It can increase to a maximum of what?
- 25-45 bpm
| - 220-250 bpm
69
Can heart rate in a horse increase rapidly or slowly?
Increases rapidly
70
What are 3 factors that can affect stroke volume?
- Myocardial contractility
- Venous return
- Blood volume
71
What are 3 factors that can affect venous return?
- Vasoconstriction
- Muscle contraction
- Changes in air pressure within the thorax
72
Splenocontraction can contribute up to how much increased volume?
12 L
73
What portion of cardiac output is limited in a horse?
Stroke volume
74
An increased heart rate leads to a decreased what?
Decreased ventricular filling time (preload)
75
How much of an increase in stroke volume is seen with submaximal exercise?
Is there any further increase with increase in exercise?
- 20-50% increase
| - No further increase
76
Which system is the limiting factor for maximal exercise?
Respiratory system
77
Ventilation is what rate at rest?
| At exercise?
- 80 L/min
| - 1800 L/min
78
What are 4 ways to increase tidal volume?
- Increasing diaphragm contractions
- Increasing pleural pressure changes
- Increasing flow
- Limit to muscular activity (energy needed to increase ventilation uses more oxygen then it delivers)
79
What is a normal pleural pressure at rest?
| During exercise?
- 5 mmHg
| - (-40 mmHg)
80
What is respiration coupled with at the canter and gallop?
| At what ratio?
- Respiration is coupled with stride frequency
| - Ratio of 1:1
81
What acts as a pump when the horse is cantering/galloping?
Visceral contents
82
When the forelegs move forward, what happens to the rib cage?
Rib cage is pulled forward and outward.
83
When bearing weight, what happens to the rib cage?
Rib cage absorbs forces and is compressed.
84
What can improve O2 extraction?
High a-v O2 gradient
85
What does a high a-v O2 gradient favor?
Favors diffusion down concentration gradient.
86
What does a right shift of O2 dissociation curve favor?
"Off loading"
87
The ability of the horse's muscle mass to consume oxygen far exceeds what?
The ability of the heart and lungs to provide oxygenated blood.
88
Conditions resulting in what positively impact performance?
Improved cardiac output
89
What is the highest percentage stroke volume can be increased by?
20-50%
90
An extremely high heart rate can lead to what?
Reduced ventricular filling time.
91
Hypoxemia ensues at what percentage VO2 max?
| What is this due to?
- 65%
| - Due to diffusion limitation
92
Diffusion limitations are due to what?
Passage of RBCs too quickly past capillaries so not fully saturated with O2.
93
Respiration rate is limited to what ratio?
| What max rate?
- 1:1 stride to RR ratio
| - Max rate: 130/min
94
What are 2 limitations to ventilation?
- Work of breathing very high
| - Use of more O2 than it delivers
95
Resistance to flow is seen more in what part of the respiratory tract?
Upper airway
96
What are 2 limitations concerning oxygen delivery to the tissues in the respiratory system?
- Resistance to flow in the upper airways
| - Diffusion impairment
97
What are 3 forms of compensation for reduced oxygen delivery to the tissues?
- Increased oxygen carrying capacity
- Increased heart rate
- Increased oxygen removal at muscles
98
What are 3 reasons endurance horses may become fatigued?
- Glycogen depletion
- Switching from Type I to Type II fibers
- Can't produce enough energy for the level of exercise
99
What are 4 factors to fatigue seen with high intensity exercise?
- Switching to Type IIX fibers
- Increasing anaerobic production
- Increasing lactate levels
- Acidosis
100
What are 2 effects of acidosis due to muscle fatigue?
- Impairs glycolysis and oxidative phosphorylation, leads to decrease ATP
- Uptake of calcium in sarcoplasmic reticulum
101
Fatigue in aerobic metabolism leading to glycogen depletion occurs in what type of fibers first?
Then what type?
- Occurs first in Type I
| - Then IIA then IIX
102
Fatigue in anaerobic metabolism is correlated with which fibers?
Type II fibers
103
What are 5 ways in which training improves oxygen delivery?
- Increase in heart mass
- Increase in SV
- Increase in PV
- Increase in total RBC volume
- Increased capillary supply to the muscles leads to increased transit time and more oxygen unloaded
104
What are 2 ways blood gets redistributed?
- Vasodilation to muscles and skin
| - Vasoconstriction to splanchnic region and non-working muscles
105
What are 5 metabolites produced by working muscles?
- K+
- H+
- Lactate
- CO2
- Heat
106
Redistribution of blood during exercise leads to an increase in what?
Increased delivery to working muscles.
107
Training can lead to what 4 muscle changes?
- More type IIA fibers
- Volume of mitochondria
- Oxidative enzymes
- Increase in glycogen stores
108
What are 2 main complaints leading to exercise evaluation?
- Poor performance
| - Exercise intolerance
109
A demonstration of clinical problems when exercising is known as what?
Exercise intolerance
110
What are 2 aspects to a fitness assessment?
- Evaluate fitness
| - Potential assessment
111
What are 3 possible causes of dynamic obstructions of the airways?
- DDSP
- Dynamic pharyngeal collapse
- Laryngeal hemiplegia
112
The incorporation of what tool has lead to a decrease in the need for treadmills?
Newer endoscopes
113
What are 2 things standard exercise tests help to assess?
- Incremental exercise test
| - Run to fatigue test
114
When assessing athletic ability what are 2 measurements taken for heart rate?
- Speed at maximum heart rate
| - Speed at which heart rate of 200 is achieved
115
What 2 measurements are made for lactate?
- Speed at which lactate reaches 4 mmol/L
| - Maximum lactate levels achieved
116
What are 2 ways to evaluate the heart for performance potential?
- Heart score
| - Echocardiographic evaluation of hear size
117
What are 3 other ways to evaluate performance potential?
- Muscle biopsy
- Inter-mandibular width
- Treadmill testing
118
Does performance rely on one characteristic or many?
Many
119
What are 7 factors of exhaustive horse syndrome?
- Protracted submaximal exercise
- Hot weather
- Loss of sweat (electrolytes and fluid)
- Dehydration
- Electrolyte disturbances
- Hyperthermia
- Energy depletion
