Exercise Physiology Flashcards
What is the athletic ability of a horse best measured by?
VO2max= HR X SV X (a-v)O2
What is the VO2max comparison of a horse to a cow?
2.5 times that of a cow
T/F: The HR, SV, and CO are all similar in equine and bovine?
FALSE- HR similar but SV and CO greater in equine
What is the at rest vs. end of race HR of a horse?
At rest: 26-44
End of race: 180-250
What % of body weight is contributed to muscle in equine?
50%
What two components of muscle are higher in the horse?
Higher concentration of glycogen and increased number of mitochondria- more aerobic work
What three factors allow for high aerobic exercise capacity?
- capacity for huge increase in O2 delivery to muscles
- increase RBC numbers
- reach greater O2 extraction than other species
How is energy supplied in initial exercise?
use of stored energy- ATP, PCr, and ADP-myokinase
What pathway generates a tremendous amount of ATP but is only sustained for a few seconds?
Phosphocreatine Pathway- used in initial seconds allowing anaerobic pathway to come up to speed
Where does anaerobic glycolysis occur in respect to the mitochondria?
External to the mitochondria-cytoplasm
When is anaerobic glycolysis used?
Submaximal activity producing lactate and ATP
What is the best use of the anaerobic glycolysis pathway?
supplement to aerobic pathway during specific segments of exercise bouts
Where do aerobic pathways occur?
Mitochondria
How much more ATP does FFA create?
3X more amount of ATP
What percentage of energy comes from aerobic metabolism in sprinting horses?
70-80%
Low intensity exercise is mostly what type of energy pathway?
mostly aerobic
At 20-30% glycogen use, the body switches to what for energy sources?
fat as substrate
What are the three forms of muscle fibers?
Type I, Type IIA, Type IIX
Which fiber has slow hydrolysis of ATP, low glycogen content, high capillary number, high oxidative capacity, seen in forelimbs and fatigue slowly?
Type I
Which fiber generates force rapidly, has large number of capillaries/mitochondria and sustain high power for prolonged periods and is seen in the hindlimb muscles?
Type IIA
Which fiber generates force rapidly, high power/limited duration and 3X faster than IIA and is seen in the hindlimb muscles?
Type IIX
What is the predictable pattern of muscle fiber usage?
Type I –> IIA –> IIAX –>IIX
What muscle fiber is only recruited near maximal intensity?
Type IIX
Fatigue in aerobic metabolism is associated with what?
Glycogen depletion-occurs first in type I fibers
Fatigue in anaerobic metabolism is correlated to what fiber type?
Type II
How is the circulating red cell volume increased in turn increasing oxygen carrying capacity?
Splenocontraction
Splenocontraction not only increases oxygen carrying capacity and RBC but also increases what else?
SV and MAP
What can occur in the vessels of a horse that is performing in 60-70% PCV range?
Sludging(increased viscosity) causing detrimental effects to the flow
What is the HR of an exercising horse?
220-240 bpm
Venous return is enhanced by what three factors?
vasoconstriction
muscle contraction
intrathoracic pressure changes
How does intrathoracic pressure change influence the flow of blood?
Thorax pressure is more negative increasing the flow from where it is coming from and traveling back to the thorax
What is the relationship between minute ventilation and speed?
Linear increase
Minute ventilation increase results from an increase in what?
RR and Tidal volume
Low tissue O2 concentration set up hgh a-v O2 gradient favoring what?
O2 off loading to tissues
Improved O2 extraction has what kind of dissociation curve?
Right shift- hypercarbia and hyperthermia and tissue acidosis
Why at intense exercise is there a limitation of oxygen uptake?
Exercise exceeding 65% VO2max will be associated with hypoxemia because the blood is traveling so fast that there is not enough time for full saturation of O2
What is the normal PaO2 in equine?
80-110 mmHg
What is the relationship between footfall and RR when a horse is at canter and gallop?
coupled in a 1:1 ratio- limiting RR to maximum of 130/min
What is the resistance to flow in the respiratory system?
Upper airway
If there is shortened diastole-how does that affect the heart?
Majority of perfusion to coronary vessels occurs during diastole. So if you shorten diastole-then you will decrease cardiac perfusion leading to arrhythmias
What is a major CVS adaptation to increased athletic performance?
heart mass increased
What is the likely muscle fiber conversion?
IIX –> IIAX –> IIA –> I&IIA –> I
The exercise capacity of a horse is limited by what?
O2 delivery and diffusion of O2 to the muscles
