Exercise Physiology

Question 1

What the 2 types of exercise?

Answer 1

• dynamic: rhythmical movement of joints and contraction/relaxation of muscles (swimming/running/cycling)
• static: maintained contraction for a length of time (weight lifting)

Question 2

What are the requirements of skeletal muscle for energy?

Answer 2

Need energy for contraction, at rest has low metabolic needs but during exercise muscles perform work so requirements increase, energy comes in form of ATP

Question 3

What are the 3 energy sources for skeletal muscle?

Answer 3

• immediate ATP from creatine phosphate, fastest supply, no oxygen used, provides store of phosphate to maintain contraction, catalysed by creatine kinase
• anaerobic glycolysis when high ATP requirements, less efficient, no oxygen used, ATP from glucose via glycolysis, forms lactate from excess pyruvate
• aerobic, oxidative phosphorylation, sustained ATP supply, uses oxygen

Question 4

What is VO2?

Answer 4

maximal oxygen uptake consumed during exercise

• during dynamic exercise using large muscle groups during a few minutes under normal conditions at sea level
• reached when oxygen consumption remains at steady state despite increased workload
• reflects aerobic physical fitness of individual and is important determinant of their endurance capacity during prolonged, sub-maximal exercise

Question 5

What is the Fick equation?

Answer 5

VO2 = Q x (CaO2-CvO2)
Q = cardiac output
CaO2 = arterial oxygen content
CvO2 = venous oxygen content
CaO2-CvO2 = arteriovenous oxygen difference

Question 6

What is the anaerobic threshold?

Answer 6

The lactate threshold - point where lactate begins to accumulate in the bloodstream, metabolic acidosis occurs and exercise endurance reduces
- varies between individuals and spots, untrained have low AT

Question 7

What are the 2 things the CVS (central vascular system) does in response to exercise?

Answer 7

• rise in CO through increased SV and HR

- redistribution of CO to active muscles

Question 8

How is HR and SV increased in exercise?

Answer 8

Sympathetic activity increased -> increased HR and vasoconstriction, positive ionotropic response on heart
Parasympathetic activity decreased
Increased venous return due to vasoconstriction -> increased EDV -> increased preload -> increased SV (Starlings)
OVERALL INCREASED CO

Question 9

How does HR and SV increase CO?

Answer 9

SV increases until fairly moderate exercise intensity reached
Further increase in CO is reached by HR increase

Question 10

How does the heart adapt to sustained long term increased blood pressure and demand?

Answer 10

Hypertrophy - increase in cardiac myocyte size

Question 11

How does hypertrophy change a healthy heart compared to a failing heart?

Answer 11

endurance, strength or combination
increased muscle mass, normal cardiac function, reversible
vs
increased muscle mass, reduced cardiac function, irreversible, cell death & fibrosis

Question 12

How does HR of athletes compare to normal individuals?

Answer 12

athletes have lower HR - bradycardia

Question 13

How does distribution of CO differ between when resting vs exercising?

Answer 13

Rest - 20-25% distributed to muscles at 1L/min

Maximal exercise - 80-90% of CO goes to muscle at 22L/min

Question 14

What are the 2 main mechanisms which control redistribution of blood flow?

Answer 14

• systemic regulation: alpha adrenoreceptors constrict gut vessels and cause vasoconstriction of veins, beta 1 adrenoreceptors in heart increase rate and myocardial contraction, beta 2 adrenoreceptors relax muscle - increase ventilation and oxygen uptake and vasodilation
• local control: local regulatory factors from blood vessels (endothelial mechanisms - NO relaxes SM cells causing dilation, tissue factors - adenosine and inorganic phosphates, carbon dioxide, H+, K+ released from contracting muscles)

Question 15

How does blood pressure change during exercise?

Answer 15

TPR drops

• increased force of contraction and SV = increase in systolic pressure
• diastolic pressure remains stable or decreases

Question 16

How does the respiratory system respond to exercise?

Answer 16

Increased pulmonary minute ventilation

(8L/minute to 100L/minute via respiratory rate rise and tidal volume) and oxygen extraction

Question 17

How do blood gases change during exercise?

Answer 17

PaO2 declines
PvO2 declines
PvCO2 rises
arteriovenous difference in oxygen rises driving oxygen diffusion into cells

Question 18

How does the haemoglobin oxygen curve change during exercise?

Answer 18

Decrease in Hb-O2 binding affinity

• increased CO2, increase H+ and increased temperature so shifts curve to the right
• increased oxygen delivery to tissues

Question 19

What is post exercise oxygen consumption?

Answer 19

Increase in rate of oxygen intake/uptake following strenuous activity following strenuous activity, as during exercise you are in oxygen debt as not enough produced quick enough, oxygen uptake reaches a level appropriate to degree of exercise but then doesn’t decline as rapidly as exercise level does to reach resting levels again for up to 60 minutes so have extended consumption for a while to make up for previous deficit
- initially in decline ATP and creatine phosphate resynthesised into glucose and glycogen

Question 20

What is the challenge of matching CO and ventilation to metabolic demands of exercise?

Answer 20

Several different feedback systems and mechanisms:

• autonomic factors (para vs symp)
• brain central command modulates baroreceptor reflex sensitivity
• metaboreceptors respond to changes in metabolite concentrations
• neural mechanisms activate respiratory muscles
• chemoreceptors as CO2 drives ventilations
• peripheral chemoreceptors initiate changes due to plasma potassium concentrations