EXERCISE AND THE HEART

Acute exercise
– Single bout of exercise
 Steady State (Submaximal) exercise
 Maximal exercise

Chronic exercise
– Months of conditioning or training
– Differences between training and untrained
individuals
Cardiovascular Response to Acute
Exercise
w Heart
rate (HR), stroke volume (SV), and cardiac
.
output (Q)...
w Blood flow (and distribution)….
w Blood pressure …
w All of the above change during exercise in
order to meet the increase O2 and energy
demands of the muscles.
Heart Rate and Acute Exercise





Why does heart rate increase during acute
exercise?
What causes heart rate exercise?
Why does heart rate level off when the
exercise intensity levels off?
What is the relationship between heart and
exercise intensity?
How is maximum heart rate estimated?
Heart Rate and Acute Exercise
Heart
Rate
Mile
Heart Rate and Acute Exercise
 What
causes heart rate to increase?
Parasympathetic
 Sympathetic
 Catecholamines

– Epinephrine
– Norepinephrine
Heart Rate and Acute Exercise
Why does heart rate level off when the
exercise intensity levels off?
 O2 supply = O2 demand

Heart Rate and Acute Exercise
Heart Rate and Acute Maximal Exercise
What is the
relationship
between heart rate
and exercise
intensity? Or, how
is heart affected by
the intensity of
exercise?
Heart Rate and Acute Maximal Exercise

Can be estimated: HRmax =
220 – age in years
–
–



Other formulas:
210 – (0.65 x age)
208 – (0.70 x age)
–
–

For 20 year old, HRmax =
200
For 43 year old, HRmax =
177
For 20 year old, HRmax =
194
For 43 year old, HRmax =
178
202 – (0.72 x age)
Stroke Volume and Acute Exercise
Why does stroke volume increase during exercise?
 What causes stroke volume to increase during
exercise?
 Why does stroke volume stop increasing, or reach
its maximum, before a person reaches their
maximal effort?
 What is cardiovascular drift?

Stroke Volume and Acute Exercise
•
What causes stroke volume to increase during
exercise? Hint: There is less residual volume
• What is residual volume?
• The amount of blood remaining in the heart after a
contraction. Also called end systolic volume
•
•
What causes the heart to beat stronger (and thus
reduce the residual volume) during acute
exercise?
Increase sympathetic stimulation and increases in
epinephrine and norepinephrine
Stroke Volume and Acute Maximal Exercise
Why does stroke
volume stop
increasing, or
reach its
maximum, before
a person reaches
their maximal
effort?
Stroke Volume and Acute Exercise
 What
is cardiovascular drift?
What happens to the amount of plasma
as exercise continues? Increase or
decrease?
 What affect would a decrease in plasma
volume have on stroke volume?
 If stroke volume decreases, what would
have to happen to heart rate in order to
keep blood flow or cardiac output at the
same level? (see next slide)

Stroke Volume and Acute Exercise
Cardiovascular Drift
Cardiac Output and Acute Exercise
If heart rate and stroke volume increase
during exercise, what will happen to
cardiac output?
 Why is it important that cardiac output
increases during exercise?
 How can even more blood be sent to the
exercising muscles?

Cardiac Output and Acute Maximal Exercise
If heart rate and stroke volume increase during exercise, what will
happen to cardiac output?
Why is it
important that
cardiac output
increases during
exercise?
Summary of HR, SV and Q During Acute
Exercise
Activity
Heart rate Stroke volume
(beats/min)
(ml/beat)
Cardiac output
(L/min)
Resting (supine)
55
95
5.2
Resting (standing
and sitting)
60
70
4.2
Running
190
130
24.7
Cycling
185
120
22.2
Swimming
170
135
22.9
Blood Flow and Acute Exercise

How can even more blood be sent to the
exercising muscles?.
Blood Flow and Acute Exercise
Blood Flow and Acute Exercise
How can even more blood be sent to the
exercising muscles?
 Vasodilation of arterioles near exercising
muscles

– Waste products

Vasoconstriction of arterioles near nonexercising muscles and organs.
– Sympathetic stimulation
Blood Pressure During Acute Exercise
How would an increase in blood flow
through the blood vessels affect blood
pressure?
 How would vasodilation of the blood
vessels affect blood pressure?

Blood Pressure During Acute Exercise
Cardiovascular Endurance Exercise
What affect does CV exercise have on
systolic blood pressure?
 Why?
 What affect does CV exercise have on
diastolic blood pressure?
 Why?

Blood Pressure During Acute Exercise
Resistance Exercise
How does resistance exercise affect
blood pressure?
 Why?
 Some BP increases are attributed to the
Valsalva maneuver

Blood Pressure During Acute Exercise
Blood Flow and Acute Exercise

What is responsible for the increase blood flow
to the muscles during exercise?
– Increased cardiac output
 Increased heart rate and stroke volume
– Redistribution of blood flow
 Vasodilation and vasoconstriction
What will happen to aerobic energy production
as more blood is supplied to the muscles during
exercise
 How is aerobic energy production measured?


Oxygen consumption or VO2
Oxygen Consumption


1.
2.

VO2 is a measure of how much and how fast
O2 is used to make energy (ATP)
In order for VO2 to increase what must change
inside the body?
Increase cardiac output
Increase extraction of oxygen from the blood
Therefore VO2 = cardiac output x the amount
of oxygen extracted from the blood
Oxygen Consumption
Oxygen Extraction at
Rest
 Arteries

– 20 ml or oxygen in every
100 ml of arterial blood

Veins
– 15 ml/100 ml of blood.
How much oxygen did
the muscles use?
 This amount is call the
a-vO2 difference.

Oxygen Consumption
Cardiac output (Q) = how quickly an amount of
blood (e.g. 100 ml) flows to the muscles
 a-v O2 difference = amount oxygen of that 100
ml is extracted (or removed) from the blood
 VO2 = Q x a-v O2 difference
 VO2 is how aerobic energy production is
measured

Oxygen Consumption
What does VO2 tell us?
 How much oxygen is being used to make
energy
 Resting VO2 = 3.5 ml/kg/min
 Exercise VO2
 Maximal VO2 (VO2 max)

Exercise VO2
VO2 (ml/kg/min)
= 57 ml/kg/min
Running = 38 ml/kg/min
Jogging = 24 ml/kg/min
Walking = 16 ml/kg/min
Time
Maximal VO2
Results from a graded treadmill test where treadmill speed and
elevation are increased every minute.
TIME
1
2
3
4
5
6
7
8
9
10
11
HR
125
138
140
147
155
164
168
174
180
186
192
VO2
VO2/KG
2096
35.52
2383
40.39
2611
44.26
2735
46.35
2957
50.12
3257
55.20
3270
55.42
3583
60.74
3813
64.63
3999
67.77
4181
67.86
VCO2
1577
2000
2295
2333
2677
2934
3041
3481
3848
4245
4704
R
0.75
0.84
0.88
0.85
0.91
0.90
0.93
0.97
1.01
1.06
1.13
VE
37.70
45.30
51.70
53.70
58.70
62.30
63.90
76.00
85.50
92.50
111.60
%EO2
%ECO2
15.78
4.20
15.97
4.45
16.13
4.47
15.88
4.58
16.10
4.61
15.92
4.76
16.00
4.81
16.36
4.63
16.58
4.56
16.68
4.65
17.17
4.29
Maximal VO2 Values
PERCENTILE
20-29
30-39
40-49
50-59
60+
Men
90
51.4
50.4
48.2
45.3
42.5
50
42.5
41.0
38.1
35.2
31.8
10
34.5
32.5
30.9
28.0
23.1
90
44.2
41.0
39.5
35.2
35.2
50
35.2
33.8
30.9
28.2
25.8
10
28.4
26.5
25.1
22.3
20.8
Women
►Average values for 18-22 year olds: 44 to 50 ml · kg-1 · min-1 for males and 38
to 42 ml · kg-1 · min-1 for females