Experimental evaluation of the differing effects of aerobic versus anaerobic exercise on post-exercise heart rate decline.

1. The Effects of Aerobic and Anaerobic Exercise on Rate of Post-exercise
Heart Rate Decline
Jessica Todd, Robin Enloe, Gwen Burkett, Suneel Moturi
Exercise Physiology Spring 2013
Abstract
Introduction
Methods
Results
Results (cont.’d) Conclusion
References
Hypothesis
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Introduction: Heart rate (HR) increases due to sympathetic
nervous system activation during exercise. It remains increased
post-exercise due to epinephrine remaining in the blood
stream. Purpose: To determine the rate at which HR returns to
resting levels after aerobic and anaerobic exercise. Methods:
We measured the rate of HR recovery for eight sedentary
individuals (ages 20-30). The subject began by resting, then
pedaled on a cycle ergometer for ten minutes (HR between
150-170 bpm). Immediately afterward, the subject returned to a
supine position and HR was recorded in 15 second intervals
until resting HR was reached. Upon the second visit the subject
performed a Wingate test while the procedure for pre- and post-
exercise remained the same. Results: Overall, it took longer for
HR to return to rest after anaerobic activity. However, the rates
of initial HR decline post-exercise was higher for anaerobic
exercise being -0.2268 bpm/sec. The rate for HR decline for
aerobic exercise was -0.2178 bpm/sec. Conclusion: The data
suggests that since HR is decreasing at a faster rate during the
initial and plateaued post-anaerobic period then epinephrine is
being removed from the system at a faster rate. However, since
it takes a longer duration for HR to return to resting values it
may be suggested that there is more epinephrine released into
the system during anaerobic exercise than during aerobic
exercise.
When performing exercise, heart rate will increase rapidly in
proportion to the exercise intensity. Exercise intensity can be used
to categorize the type of exercise your body is performing,
specifically aerobic and anaerobic exercise. Both types of exercise
use different methods to produce energy required to perform the
task. Anaerobic exercise uses glycolysis and phosphocreatine
(ATP-PCr) systems, whereas aerobic exercise uses oxidative
systems. Heart rate (HR) increases during anaerobic and aerobic
activity due to sympathetic nervous system activation. During
exercise the sympathetic nervous system is stimulated, which
causes a release of epinephrine and norepinephrine. These
neurotransmitters are continually released until exercise is
ceased, and they will remain in the blood until the body returns to
resting conditions. The duration norepinephrine remains in the
blood stream is directly proportional to HR recovery time. After
exercise, parasympathetic stimulation is increased to help return
the body to rest.
We hypothesized that the rate of heart rate decline post-exercise
will be higher after anaerobic exercise rather than aerobic
exercise.
This experiment studied eight sedentary men and women. The
subjects were nonsmokers between the ages of 20 and 30. We
measured resting, exercise, and recovery heart rate (HR) using a
heart rate monitor and wrist telemetry watch. Both aerobic and
anaerobic exercise took place on a cycle ergometer. Prior to
exercise the subject rested for ten minutes. The aerobic test
consisted of a ten minute aerobic workout with heart rate
remaining between 150-170 bpm. The anaerobic test consisted
of a Wingate test and accompanying recovery periods for each.
Heart rate was recorded at the end of resting, the end of exercise
and then every 15 seconds during recovery until resting HR was
reached. To control time of last meal, all subjects will need to fast
for two hours prior to the experiment. To control the amount of
sympathetic outflow, the subjects will be instructed to refrain from
exercise, consumption of liquor or caffeine, and ibuprofen or
other pain medicine after midnight (morning of the experiment).
Figure 1 shows the data collected for one subject’s anaerobic
and aerobic tests. Figure 2 compares average rates of recovery
for each individual. Figure 3 displays our final results: the rate in
which HR decreased post-exercise was greater after anaerobic
exercise being -0.2268bpm/s for the initial decline. Initial aerobic
decline was -0.2178bpm/s. The trend continued in the plateaued
decline being-0.1311bpm/s for post-anaerobic exercise and
-0.1233bpm/s for post-aerobic exercise.
Figure 1. The effect of time on post-exercise heart rate.
Figure 2. Comparison of individual anaerobic and aerobic
recovery rates.
Figure 3. Comparison between average anaerobic and aerobic
rate of recovery.
This experiment sought to discover how heart rate (HR) recovery
differs after anaerobic exercise versus aerobic exercise.
Anaerobic exercise entails high-intensity, short duration activity.
Aerobic exercise entails a lower intensity, longer duration
activity. During exercise the sympathetic nervous system is
activated which causes an increase in heart rate (3-5).
Epinephrine travels through the blood and remains therein
temporarily post-exercise; this accounts for the delay in heart
rate returning to rest. Conversely, the parasympathetic nervous
system is activated post-exercise to return heart rate back to rest
(3-4).
The negatively sloped trend lines in Figure 1 represent the rate
of decline in HR. The data supported our hypothesis in that the
rate of HR recovery was faster after anaerobic activity. Figure 3
shows that the average rate for recovery after anaerobic
exercise is -0.2268bpm/s while that after aerobic exercise is
-0.21778bpm/s. The data suggests that since HR is decreasing
at a faster rate during the initial and plateaued post-anaerobic
periods, then epinephrine is being removed from the system at a
faster rate. However, since it takes a longer duration for HR to
return to resting values it may be suggested that there is more
epinephrine released into the system during anaerobic exercise.
The extra epinephrine would be released due to the additional
stress of peak performance (5). If so, then more remained in the
blood post-exercise that caused heart rate to remain elevated
longer. It is possible that parasympathetic activation post-
anaerobic exercise is subdued or completely absent (2). The
plateau illustrates heart rate decreasing solely by withdrawal of
sympathetic stimulation, therefore prolonging its effects (1-2).
However the amount of epinephrine released during each type
of exercise remains elusive.
We can see in Figure 2 that not all subjects support our
hypothesis. Some of the factors limiting the experiment include:
excessive noise, presence of light, restlessness, and physical
disturbances (i.e. bed being bumped). To control for these
limitations, the experiment should be conducted in a more
isolated environment.