Conducting an experiment to determine the correlation between using caffeine and its effects on heart-rate

Introduction

Caffeine has been known to affect the human body in a multitude of ways. Caffeine is often associated with being responsible for insomnia, raising blood pressure, headaches, nervousness, as well as a jittery feeling (Food and Drug Administration 1). However, caffeine also has some positive effects as well. Caffeine can assist with encoding new information as well as counteracting fatigue when taking part in mentally and physically straining tasks (Smith, Clark, and Gallagher 9). This experiment was conducted in order to determine if ingesting caffeine before physical activity will affect the heart rate.

It was hypothesized that ingesting caffeine prior to physical exercise will cause the subject’s heart rate to take longer to return back to their resting heart rate than those who did not ingest any caffeine. This hypothesis was drawn due to caffeine’s tendency to increase stress in the body, such as high blood pressure and shakiness. I suspect that test subjects who consume caffeine prior to physical activity will take considerably longer to return to their resting heart rate opposed to those did not consume any caffeine

Materials and Method

In this experiment, four test subjects were monitored.

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Two test subjects consumed caffeine prior to the test and two test subjects did not consume any caffeine prior to the test. First, personal information was recorded for all four test subjects.

The age, gender, hours slept, hours since eating, caffeinated beverages consumed, weight, and height were recorded for each test subject. Next the resting heart rate was recorded for all four test subjects. Test subjects counted the number of pulses in the artery on either the wrist for the next for a total of 15 seconds. This number was then multiplied by four to determine the resting heart rate. After all of this data has been collected, the first of two tests was conducted. In test 1 test subjects 3 and 4 ran up and down a flight of stairs at a consistent pace for two minutes. Then, the heart rate of each test subject was recorded immediately after completing the physical activity. Their heart rate was then measured at 2 minutes after the activity, 5 minutes after, 10 minutes after, and 15 minutes after. This process was then repeated in test 2 with test subjects 1 and 2.

Results

The experiment went as expected with no unpredicted events that would have introduced error. In test 1 test subject 3 had a resting heart rate of 76 bpm. Immediately after completing the physical activity the test subject’s heart rate rose to 124 bpm. Two minutes after the activity subject’s heart rate dropped to 92 bpm. Five minutes after the activity the test subject’s heart rate dropped to 84 bpm. Ten minutes after the activity the test subject’s heart rate dropped back down to their resting heart rate of 76 bpm. In test 1, test subject 4 had a resting heart rate of 74 bpm. Immediately after completing the physical activity the test subject’s heart rate rose to 124 bpm. Two minutes after the activity the test subject’s heart rate dropped to 100 bpm. Five minutes after the activity the test subject’s heart rate dropped to 84 bpm. Ten minutes after the activity the test subject’s heart rate dropped back down to their resting heart rate of 74 bpm. In test 2, test subject 1 had a resting heart rate of 78 bpm. Immediately after completing the activity the test subject’s heart rate rose to 134 bpm. Two minutes after the activity the test subject’s heart rate dropped to 115 bpm. Five minutes after the activity the test subject’s heart rate dropped to 108 bpm. Ten minutes after the activity the test subject’s heart rate dropped to 102 bpm. Fifteen minutes after the activity the test subject’s heart still had not returned to their resting heart rate. After fifteen minutes, test subject 1’s heart rate was 97 bpm. In test 2, test subject 2 had a resting heart rate of 80 bpm. Immediately after completing the physical activity the test subject’s heart rate rose to 152 bpm. Two minutes after the activity the test subject’s heart rate dropped to 112 bpm. Five minutes after the activity the test subject’s heart rate dropped to 96 bpm. Ten minutes after the activity the test subject’s heart rate dropped to 92 bpm. Fifteen minutes after the activity the test subject’s heart rate still had not returned to their resting heart rate. After 15 minutes, test subject 2’s heart rate was 88 bpm.

Subject Resting Heart Rate Heart Rate Immediately After Activity Heart Rate 2 Minutes After Activity Heart Rate 5 Minutes After Activity Heart Rate 10 Minutes After Activity Heart Rate 15 Minutes After Activity

1 78 134 115 108 102 97

2 80 152 112 96 92 88

3 76 124 92 84 76 ---

4 74 124 100 84 74 ---

Figure 1 heart rates after completing physical activity

Figure 2 caffeine’s effect on heart rate

Discussion

Based off of the data recorded in this experiment, one can conclude that caffeine does not have an effect on how long it takes for a person’s heart to return back to their resting heart rate after participating in a physical activity. It seems that the in both tests the test subjects’ heart rates decreased at approximately the same rate. However, it takes longer for those who consumed caffeine to return to their resting heart rate after participating in a physical activity because their initial heart rate immediately after the activity was considerably higher than those who did not consume caffeine.

This is not surprising given the fact that caffeine consumption does cause the body to undergo a higher level of stress. Caffeine is associated with causing people to become jittery and nervous as well as increasing blood pressure (Food and Drug Administration 1).

However, there may be benefits in raising your heart rate during exercise. For ages 20-29, the ideal heart rate during exercise is between 100-170 bpm. For ages 30-39, the ideal heart rate during exercise is between 69-162 (American Heart Association). Therefore, increasing a person’s heart rate prior to exercise could be beneficial if done in moderation.

Consuming caffeine prior to exercise has also been supported by other studies as well. In a study conducted by O’Rourke et al., both well-trained and recreational runners showed an increase in performance when consuming caffeine prior to running. In this study the runners had to complete a 5 kilometer run. Half of the runners were randomly selected to be given 5 mg of caffeine and the other half received a placebo. Runners who consumed caffeine prior to exercise were 1.4% faster than those who received the placebo. The researchers concluded that caffeine consumption prior to physical activity can produce small, but significant, gains.

The study conducted by monitoring caffeine’s relationship with heart rate did not supports my original hypothesis that stated it would take longer for a person’s heart rate to return to their resting heart rate after participating in a physical activity as opposed to those who did not consume caffeine. The information revealed that caffeine only increases a person’s heart rate immediately after physical activity, but the heart rate still decreases at about the same rate as those who did not consume caffeine. These results will be a helpful aid in providing a method in which a person can exercise at their optimum heart rate, as well as defining safe heart rates to maintain during exercise when consuming caffeine.