1. Laboratory for Physiology
ECG
Cardiovascular System and Exercise

2. Before, during and after exercise
Introduction
a. Today we will look at how the cardiovascular system responds to accommodate the increased metabolic demands of the skeletal muscles during exercise
b. To do this you will record your subjects:
ECG
Blood Pressure
Skin temperature
Before, during and after exercise

3. Introduction
Exercise for this lab is going to be a step test where the subject will step up and down at a rate of about steps/minute for 9 minutes
This is a quick pace and should cause a good cardiovascular response in most people
Every 3 minutes you will record your subjects ECG, Skin Temp and systolic BP. Overall you should have 7 measurements when you are done:
Parameters at rest
After 3 minutes of exercise
After 6 minutes of exercise
After 9 minutes of exercise
Immediately Post-excercise
Recovery period: 2 mins post exercise
Recovery period: 5 mins post exercise

4. Potential problems Sweating causes electrodes to come loose
Solution: Tape the ECG electrodes in place with water proof tape and fan to keep cool
Noise in the recording due to movement during the exercise stage
Solution: Try to minimize movement of the cables by taping them in place on the carts.
Taking the subjects BP during exercise
2 Ways:
Feel pulse. Blow up the cuff until you can’t feel the pulse any longer. This is approx SBP.
Inflate cuff and gradually release pressure and watch for the pot that the needle starts to beat. Record this as SBP
Whichever method you chose you should PRACTICE each BEFORE you start the lab exercise.

5. Expected Results
When a person exercises the normal homeostatic mechanisms’ that serve to maintain BP are over-ridden by the brain so that the demands of the exercising tissues can be met
When a person starts exercising inputs to the CVCC from the higher brain cause
INCREASED Sympathetic activity
DECREASED Parasympathetic activity

6. Which has FOUR effects on the cardiovascular system
INCREASED HR
INCREASED Stroke Volume (SV) and Cardiac Output (CO) of the heart
Re Distribution of Blood flow and Vasoconstriction of the arterioles is caused by the increased Sympathetic activity
HEAT

7. INCREASED HR HR is controlled by the pace maker cells in the SA node
These cells receive both sympathetic and parasympathetic inputs
Para SLOWS HR
Symp SPEEDS up HR
At rest Para tends to dominate generating a resting HR of ~70-80 bpm
As you exercise the CVCC under the influence of higher brain centers adjusts the balance between Symp and Parasympathetic such that there is a decrease in Parasympathetic and an increase in Sympathetic activity
PARASYMPATHETIC HR
SYMPATHETIC

8. INCREASED Stroke Volume (SV)
SV is the volume of blood ejected by the LV contraction
SV depends to a large degree on the force of contraction of the heart
Force of contraction = SV
Heart musculature receives input from the Sympathetic nervous system which acts to adjust the force of contraction (contractility) of the heart muscle
Increased Sympathetic inputs during exercise induce an INCREASE in the force of contraction which in turn INCREASES stroke volume
Sympathetic Activity = Force of contraction = SV

9. INCREASED Cardiac output (CO)
The volume of blood pumped/unit time.
CO is determined by the product of HR+SV and so can be calculated using the formula:
CO=HR X SV
During exercise
HR SV = CO
***This means that during exercise more blood is being delivered to the arterial system/unit time which is reflected as an increase in systolic BP
During exercise CO is not distributed evenly to all the organs of the body. Rather it is directed to where it is needed most (i.e. the active muscles) This selective redistribution of blood during exercise is achieved by the COMBINED AFFECTS of
1. The INCREASED sympathetic activity
2. Release of local vasodilators (CO2, Lactic acid) in the exercising muscles. Redistributed bloodflow is the 3rd effect seen during exercise.

10. Re Distribution of Blood flow and Vasoconstriction of the arterioles is caused by the increased Sympathetic activity
This decrease in blood flow to the skin yields a DECREASE in skin temperature
The muscles are initially also vasoconstricted but as they exercise they release local vasodilators (CO2, Lactic Acid) leading to increased blood flow.
Vasodilation of the vasculature that supply these muscles DECREASES resistance to blood flow in these vessels so blood is directed away from the vasoconstricted vessels in the skin and other parts of the body and rather directed towards the vasodilated vessels in the muscles where it is needed.

11. HEAT During sustained exercise heat builds up in the body
THUS a decrease in blood flow to the skin causes the core body temperature to rise. This rise in BT is sensed by temperature sensors in the hypothalamus which activates a part of the sympathetic system called the SYMPATHETIC CHOLINERGIC VASODILATOR SYSTEM.
The SCVS acts to selectively dilate the blood vessels in the skin
This increased blood flow to the skin allows for increased heat loss across the skin
During the early stages of exercise skin temp DECREASES due to DECREASED blood flow but during sustained exercise skin temperature INCREASES as the SCVS is activated and blood flow is re directed to the skin.
During this lab you should watch for these changes in skin temp, HR and SBP.

12. HINTS: Tape the thermistor to the finger Tape electrodes to the chest
Make sure temp is stable BEFORE starting to exercise This may take 5-10 minutes!
Tape electrodes to the chest
Clip cables to subjects clothing to minimize movement
Tape cables to cart to minimize movement of cables during exercise
BEFORE your subject starts exercising, test to make sure you are getting good readings on the Biopac and practice taking their SBP
If subjects HR exceeds their calculated max HR they should slow their exercise rate but NOT STOP
If the subject can’t complete the exercise then they may voluntarily stop but try to do your best to keep going.

13. Enjoy the lab HAVE FUN DO NOT RUSH!!!!!
QUESTIONS?
Enjoy the lab
HAVE FUN
DO NOT RUSH!!!!!