Download Cardiovascular response to exercise

SPS2201 – Exercise Physiology
Laboratory Report 3
Cardiovascular Response to Exercise
Greg Levin
Student Number: 2011360
Edith Cowan University
1.0
Introduction
The added stress placed on the body during exercise causes many changes to
occur within the body. In fact Laughlin (1999,p. 244) explains that dynamic exercise
places more stress on the cardiovascular system than anything else. One of the most
important changes is the response of the cardiovascular system to deal with the
increased amount of blood and oxygen required by the working muscles (Wilmore &
Costill, 1994, p. 176). The way in which the system responds can be seen by changes
in heart rate, blood pressure, and ECG.
1.1
Aim
To view if changes in the heart rate, blood pressure, and ECG are a direct
result of varying workloads.
2.0
Method
2.1 Participants
In order to test for any variation between males and females, two participants
took part in the test. ‘Subject 1’ was a male in his early to mid-twenties and ‘subject
2’ a younger female in her late teens. Neither of the subjects were elite athletes
although both exercise regularly.
2.2 Materials
The equipment that was required to carry out the test included a Repco cycle
ergometer, a PE 4000 heart rate monitor and IBM computer interface, a
sphygmomanometer and stethoscope, and a stopwatch.
2.3 Procedure
The participant was seated and a resting blood pressure (BP) and resting
heart rate (HR) was recorded. A three lead ECG was attached to the subject in order
to take recordings of the heart activity. The ergometer was then adjusted to suit the
physique of the subject. Once seated on the ergometer another set of BP and HR
readings were recorded. The participant then began cycling at a workload of 50 watts.
At the completion of three minutes the workload was increased to 100 watts and then
again at the end of the next three minutes the workload was increased to 150 watts.
The participants HR was monitored and recorded every minute while ECG and BP
were only recorded at the end of every three-minutes. Upon completion of the 9
minutes the participant was instructed to continue cycling for a further three minutes,
a cool down period, at a decreased workload of 50 watts. As before the HR was
recorded at every minute of the cool down and the BP and ECG were recorded only at
the end of the three minutes. This was repeated for both participants.
Due to a testing fault the male subject’s workloads increase was greater than 50 watts.
3.0
Results
As expected there was an increase in both heart rate and blood pressure of
both subjects. Systolic blood pressure increased by 74mmHg and 59mmHg in the two
subjects (see Table 1) and there was also a constant increase in heart rate as the
workload increased (Figure 1). Initial heart rates were 65bpm and 70bpm while the
maximal heart rates were 177bpm 184bpm respectively. The initial blood pressure of
subject 2 was taken three times because of difficulty in hearing both the systolic and
diastolic pressures and therefore the figures might be slightly inaccurate.
Table 9
Blood Pressure Responses to Increasing Workloads
Workload
(Watts)
0
0ª
50
100
150
50
Subject 1
Subject 2
124/90
114/76
124/68
176/68
188/72
164/70
110/55
111/60
150/65
160/65
170/70
140/60
ª Second blood pressure taken while sitting on the bike.
Heart Rate (bpm)
Heart Rate: Subject 1 (bpm)
Heart Rate: Subject 2 (bpm)
200
180
160
140
120
100
80
60
40
20
0
0
0
50
100
150
50
Workload (watts)
Figure 1. Heart rate responses to varying levels of exercise
4.0
Discussion
The heart rate and blood pressure were recorded twice while the subject was
not doing any work. The first recordings were a the subjects true resting heart rate and
blood pressure, whereas the second set of recordings were taken once the subject had
already seated him/herself on the bike. Usually increases are seen between resting
heart rates and the newer rates recorded just prior to exercising (Wilmore & Costill,
1994, p. 177). Unfortunately neither of the subjects showed any signs of the
anticipatory increases. This could be as a result of the subjects knowing that they were
going to partake in the tests.
Both subjects exhibited similar signs and responses to the exercise. Despite
subject 1’s workload increasing more than the desired 50 watts a comparison could
still be drawn between the two subjects. The systolic blood pressure increased slowly
and then climbed steeply as the intensity levels became harder. This was similar to
what Man-I and Imachi (1981, p. 103) described when they said, “the measurement of
both blood pressure and heart rate react greatly but slowly to exercise in untrained
subjects.” Even though both subjects do exercise regularly neither of them is trained
in cycling, and therefore fall into the category of untrained athletes. Diastolic blood
pressure on the other hand was almost unchanged. This is consistent with previous
findings and studies on the effects of exercise on blood pressure (Laughlin, 1999, p.
249). Heart rate increases matched the increase in workload and appeared at near
maximal levels for both subjects. Maximal levels were calculated at 220 minus
participant’s age (Wilmore & Costill, 1994, p. 177).
An increase in the amount of blood needed in the body causes an increase in
blood pressure. This is because the heart must pump more blood out of the heart at
each contraction increasing the systolic pressure (Wilmore & Costill, 1994, p. 169).
Although the use of a manual sphygmomanometer during exercise has caused concern
about its accuracy, it is still a suggested method (Griffin, Robergs, &Heyward, 1997,
p. 153). A problem that does arise however is that manual sphygmomanometry takes
approximately 50 seconds, a time period that was too long, and caused an overlap in
intensity differences.
Resting ECG’s showed a large gap between the ‘P’ and ‘T’ complexes. This
gap symbolises the amount of time that the heart takes between ventricular
repolarisaion and atrial depolarisation. When the exercise intensity was raised the gap
between the two became shorter signifying that the heart was working at a much
faster rate. The contracting of this gap was visible best the rest and commencement of
exercise. This indicates that the body needs to adjust as quickly as possible. Another
clear indication on the ECG was that the returning of the heart to rest patterns, during
the cool down period.
Recovery rates of the 2 subjects varied. Some cause of this might be because
of the fact that subject 1 worked at greater intensities and therefore was more
fatigued. However both subjects showed declines in their systolic blood pressures and
their heart rates. The rate at which these decline may be attributed to the level of
fitness and level of training of the athlete but neither was relevant in this case.
In conclusion, the test performed was successful in attaining the goals that were set
out. However due to the levels of inexperience amongst the testers not all information
can be regarded as being extremely accurate. Therefore while this test does show the
changes associated with the cardiovascular system in response to exercise, past and
future results are more reliable.
References
Griffin, S.E., Robergs, R.A., & Heyward, V.H. (1997). Blood pressure measurement
during exercise: a review. Medicine and Science in Sport and Exercise, 29(1),
149 – 158
Laughlin, M.H. (1999). Cardiovascular response to exercise. American Journal of
Physiology, 277, S244 – S259
Man-I, M., & Imachi, I. (1981). Effect of training on blood pressure and heart rate
measured continuously during exercise. The Journal of Sports Medicine and
Physical Fitness, 21(2), 102 – 111
Wilmore, J.H., & Costill, D.L. (1994). Physiology of sport and exercise. USA:
Human Kinetics