Exercise Physiology

Question 1

what is resting VO2?

Answer 1

250 ml/min= 1 MET

Question 2

waht is needed to translate VO2 into calories?

Answer 2

need to know caloric equivalent of consuming 1 L of oxygen. this is determined by which types of fuels are being metabolized

Question 3

how can the types of fuels being utilized be determined?

Answer 3

if the respiratory quotient is known (VCO2/VO2)

Question 4

what is the Kcal/ L O2 yield from carbohydrate, fat and protein oxidation? what are their associated respiratory quotients?

Answer 4

CHO- 5.05 Kcal/LO2 RQ=1
fat- 4.70 Kcal/ LO2 RQ=0.7
protein- 4.5 Kcal/LO2 RQ= 0.8

Question 5

how many Kcal are in a gram of CHO, fat and protein?

Answer 5

CHO and protein are 4 Kcal/gm and fat is 9.1 Kcal/gm

Question 6

what is the RER (respiratory exchange ratio)?

Answer 6

the respiratory quotient when the body’s total O2 content stays constant (unusual) and when the total CO2 content stays consant (dependent upon breathing)

Question 7

how can an accurate measure of caloric expenditure be made? what is the conversion factor used for exercise studies?

Answer 7

by measuring VO2 and RER and assuming steady state conditions exist for carbon dioxide. exercise studies use 5 Kcal/L of O2 consumed

Question 8

what does the RER estimate?

Answer 8

it is assumed that there is a negligible contribution by protein to energy production. provides an estimate of relative amounts of CHO vs fat being consumed

Question 9

what is the RER at rest? what does that predict of the distribution of energy expendature?

Answer 9

it is 0.85

predicts that 50% of the energy being used is coming from fat and the other from CHO

Question 10

how is VO2 assessed in an exercise study?

Answer 10

inspired and expired air is passed through a flow meter and oxygen and CO2 gas analyzers
VO2=Vi x FiO2 - Ve x FeO2 (corrected by computer and reported as volumes occupied at STPD)

Question 11

how does VO2 vary with work rate?

Answer 11

VO2 increases linearly with exercies intensity with increasing work rate. this increase will eventually plateau at max VO2

Question 12

what does max VO2 indicate?

Answer 12

it is the best indicator of aerobic fitness or endurance performance

Question 13

what limits VO2 max?

Answer 13

pulmonary factors- ventilatory capacity and diffusion
cardiovascular factors- cardiac ouput, distribution of cardiac output and capillarity of skeletal muscle
muscle factors- mitochondrial content

Question 14

how does total minute ventilation change during a graded exercise test?

Answer 14

it increases linearly to the point of the ventilatory threshold and then increases out of proportion to VO2 at high work intensities

Question 15

what are three things that are not responsible for the linear response phase in a graded exercise test?

Answer 15

changes in arterial PO2, PCO2 or H+

Question 16

what is the purpose of hyperventilation at higher intensities of exercise?

Answer 16

it decreases alveolar and arterial PCO2 to manage arterial pH that decreases due to lactic acidosis

Question 17

other than increased breathing rate, what contributes to effective gas exchange during exercise? what changes in ventilation occur with increasing levels of aerobic fitness?

Answer 17

increase in the V/Q ratio in most alveoi.

ventilatory threshold as a percent of VO2 max increases with increasing levels of aerobic fitness

Question 18

how does cardiac output change with VO2 during exercies? how does it compare to resting?

Answer 18

cardiac output increases linearly with increasing work intensity and VO2. max values are 4-5x resting

Question 19

how does heart rate increase with increasing VO2?

Answer 19

there is a linear relation ship. SNS input to the SA node increases with increasing stress of exercise

Question 20

how does stroke volume change with exercise?

Answer 20

it increases with mild to moderate exercise intensity and then levels off or may decline slightly at higher work rates.

Question 21

what causes increased stroke volume with exercise?

Answer 21

increases as venous return and contractility of the heart are stimulated

Question 22

how does distribution of cardiac output change with exercise?

Answer 22

arterioles to active skeletal muscles dilate so these tissues receive 80-85% of total output while there is a decrease in flow to inactive muscles and splanchnic area

Question 23

how does oxygen extraction change as exercise intensity increases? what causes this change?

Answer 23

much more oxygen is extracted with little change in arterial PO2. due to better capillary perfusion, decreased myocyte PO2 and a right shift in oxygen-Hb dissociation curve

Question 24

what is VO2 max limited by?

Answer 24

cardiac output in normal healthy individuals because muscles will use all of the O2 they can get.
in highly deconditioned individuals, ability of skeletal muscle to consume O2 may limit (bed rest, COPD)

Question 25

what does blood pressure response during exercise depend on?

Answer 25

muscle mass being used, whether the exercies is static or dynamic, body position and temperature

Question 26

why does blood pressure increase during exercise? does systolic or diastolic change more?

Answer 26

CO increases more than peripheral resistance decreases. causes a change in systolic blood pressure while diastolic pressure remains the same or changes very little .

Question 27

how does blood pressure changes during exercise vary with muscle group?

Answer 27

in arm exercises, MAP increases more than during leg exercises because the peripheral resistance increases more.

Question 28

why does MAP increase more during an arm workout than when using legs?

Answer 28

legs have vasodilation in large muscle groups and vasoconstriction to small muscle groups while arm exercises vasodilate small muscle groups and constrict the larger inactive ones

Question 29

at what points do static contractions begin to occlude blood flow? when do they stop it completely? what does this indicate for static vs dynamic exercise?

Answer 29

at 30% of maximal tension there is occlusion and there is total occlusion at 70% of maximal voluntary contraction. this means that there is higher resistance with static exercise compared to dynamic resulting in higher increase in blood pressure