The Cardiovascular Impact of Exercise
By Haley Mitchell
Abstract
The literature stated that exercise should have an effect on pulse rate, blood pressure, P-T intervals, T-P intervals, and pulse lag because it requires a higher demand of oxygen. In this experiment, we compared the differences and similarities of two different treatments. The first treatment was determined to be the values of the variables before moderate exercise and the second treatment was tested after exercise. The exercise that was decided upon was thirty jumping jacks and we compared the rates by using a digital sphygmomanometer and an ECG monitor and then performing a chi-squared test. When measuring the values related to the heart we used a lead known as Lead 1. After recording and analyzing all the data, we were concluded that exercise did not play an important role based on our results because the only variable that was effected by exercise was the P-T interval. These results went against our predictions that were made before the experiment.
Introduction
This experiment was performed with a purpose to determine whether exercise has an immediate effect on the circulatory and respiratory systems. We determine the effect from exercise by examining multiple variables before and after exercise was performed. These variables were pulse rate, systolic blood pressure, diastolic blood pressure, P-T interval, T-P interval, and the pulse lag.
According to the literature, the average heart rate of a female at rest is between seventy-two and eighty and the average heart rate for a male at rest is between sixty-four and seventy-two. It is also said that a physically fit individual usually tends to have a lower heart rate while at rest. An individual can have a resting heart rate of about forty beats per minute if that individual is a well-trained athlete. According to the conclusions of Marieb (1989), the heart rate of a healthy individual tends to be less than sixty beats per minute and a heart rate above one hundred tends to be unhealthy. This unhealthy heart rate can eventually lead to a heart problem known as ventricular fibrillation. The resting heart rate of a human is very valuable because it helps determine if there are any risks for heart attacks and cardiovascular problems (Jouven et al., 2005). Exercise causes a change in an individual’s heart rate. It causes an increase in heart rate because it stimulates the sympathetic nervous system. This stimulation then increases the speed at which the SA node is depolarized (Guyton, 1985). An individual’s heart rate is also age dependent. According to the function of age, a person’s maximum heart rate decreases as their age increases (Goodman, 1999). Each age group has a different target heart rate when exercising. Since heart rate decreases with age, so does this target heart rate. The target heart rate is a value at which the heart rate must meet in order for physically improvement. The speed at which a person’s heart rate returns to its resting value is extremely vital in a human’s health (Borresen and Lambert, 2008). If the speed at which the heart rate returns to resting is slow, then it is said that that person has a higher mortality. The resting period of the heart can be measured by the T-P interval. This interval should decrease after enough exercise is performed because of the fast speed of the contractions. The P-T interval should also decrease if a high intensity workout is performed. The shortening of the time between the start of the P wave and the terminal end of the T wave is a normal response to exercise (Goodman, 1999, p.72) Pulse lag is determined by the time difference between the moment when a ventricular depolarization occurs and the moment when a pulse of blood reaches the finger (Kosinski, 2016). This value should decrease with exercise because the heart is pumping faster which then makes the depolarization of a ventricle happen faster.
Exercise corresponds to an increase in the velocity of blood. This increase is due to the fact that there is an increase in cardiac output. Cardiac output increases during exercise because of the vasodilation in the muscles and the squeezing of the veins (Laughlin 1999). These two effects cause blood to return to the heart faster. As mentioned above, during exercise the working muscles undergo vasodilation but the rest of the body undergoes vasoconstriction (Guyton, 1985). This then means that blood pressure will increase, but this increase will depend on the amount and type of exercise. When an exercise that only requires a few muscles is performed there is a greater increase in blood pressure compared to a whole body workout. This effect is because the amount of vasoconstriction and vasodilation occurring in the body is nearly equal.
My explanatory hypothesis states that exercise leads to high demands on the circulatory and respiratory systems in order to supply more oxygen to the muscles. We used this explanatory hypothesis to predict the outcome of this experiment. We predicted that there would be a change in pulse rate, systolic blood pressure, diastolic blood pressure, P-T interval, T-P interval, and pulse lag after moderate exercise was performed. My research hypothesis for the experiment included multiple things. The research hypothesis was that the rates of the dependent variables would be different before and after moderate exercise was completed. These variables include the pulse rate, systolic blood pressure, diastolic blood pressure, P-T interval, T-P interval, and pulse lag. This hypothesis leads to the six different null hypotheses. The first null hypothesis is that the pulse rates before and after moderate exercise will be the same. The second null hypothesis is that the systolic blood pressure will be the same before and after exercise. The third null hypothesis is that the diastolic blood pressure before and after exercise will be the same. The forth null hypothesis is that the P-T interval will stay the same before and after exercise. The fifth null hypothesis is that the T-P interval will remain the same before and after exercise. The sixth null hypothesis is that the pulse lag will be the same after exercise as it was before exercise. During this experiment the independent variable will be the exercise that is performed. This exercise was performing thirty jumping jacks. The controlled variables were that there was an equal amount of males and females within the same age.
Materials and Methods
In order to perform this experiment you will need to be familiar with the scientific method and the principles of experimental design. To begin we needed to determine our explanatory hypothesis. After that we had to determine what our independent, dependent, and controlled variables were. Then we had to make predictions about the experiment and use those predictions to devise a null hypothesis.
Using the procedures from the lab handout of Kosinski (2016), we first evaluated our resting systolic and diastolic blood pressures. In order to evaluate this value we used a digital sphygmomanometer. To use this device you first have to roll up your sleeve. Then you must slip the cuff around your arm while insuring that the hose is coming out of the end facing the joint of your elbow. After placing the cuff on, you must then press the start button. After the inflation and deflation has completed, the values for diastolic and systolic blood pressure will appear. The systolic blood pressure is the value on top and the diastolic blood pressure is the value on bottom. We then had to record the values. After determining those values we then moved on to the ECG. To begin this part of the experiment we first had to turn on the computer and interfacing box. When then had to open the “Individual Cardiovascular Data” spreadsheet and “LoggerPro 2.2” icon. Then we had to open the “EKG and Heart Rate” link that was located in the “Sample Data” and “Biology” folders. The next step was to attach the ECG electrodes. To begin attaching the electrodes, we first had to place three adhesive electrodes. The first electrode was placed on the right upper arm, the second was placed on the left upper arm, and the third was placed on the right wrist. While attaching the adhesive electrodes we had to insure that the free tabs were facing toward our hands’. After attaching the adhesive, we then attached the wires. The green wire was attached to the right upper arm, the red wire was attached to the left upper arm, and the black wire was attached to the right wrist. Next we placed the pulse diode to the tip of the left little finger. We had to insure that the light was over the finger nail and that if the nails were long or fake that the diode was placed in a correct positon in order to receive an accurate reading. Then while the individual was relaxed we began the reading by clicking on the “collect” button. After the reading was complete, we then detached all the wires and pulse rate diode. Next we had to start determining the values. To begin evaluating we first had to press the “x = ?” button so that a vertical line appeared in order to help determine the time values. We determined the values for the pulse first. To do so, we placed the cursor over the first QRS complex and the last QRS complex. We recorded these time values into the cardiovascular spreadsheet. Then we counted the number of pulse peaks and determined the average pulse rate. These values were also recorded into the spreadsheet. We then measured the QRS/pulse lag. To do so we first determined the time at which the first peak of the QRS complex occurred. Then we placed the cursor at the first pulse peak after that QRS in order to determine the time. We then recorded these values in the spreadsheet in their appropriate location. The first value goes under “QRS Peak” and the second value goes under “Pulse Peak”. This process was then continued for all the QRS peaks and pulse peaks. Next we determined the P-T interval. To begin, we placed the cursor over the beginning of the first P wave and recorded this time under “Start P” in the spreadsheet. Then we placed the cursor at the end of the T wave that followed the previous P wave and we recorded this under “End T” in the spreadsheet. This process was also continued for all the P and T waves. Next we determined the T-P interval. To begin we placed the cursor over the end of the first T wave and recorded this data into the spreadsheet under “End T”. Then we positioned the cursor at the beginning of the following P wave and recording the time value under “Start P”. This method was continued until all the T and P waves were measured. After all the above information was completed, the same individual then had to perform thirty jumping jacks. Immediately after exercise, the individual’s blood pressure needed to be taken. Also immediately after exercise, the three wires needed to be reconnected to the adhesive electrodes and the same process from above needed to be performed.
Results
Table 1. Values for the average before and after rates, chi-squared, and P-Values for pulse rate, pulse lag, P-T interval, T-P interval, systolic blood pressure, and diastolic blood pressure.
Variable Before Mean After Mean Chi-Square P-Value
Pulse Rate 75.4 bpm 85.3 bpm 1.64 0.2
Pulse Lag 0.366 sec 0.344 sec 2 0.157
P-T Interval 0.643 sec 0.595 sec 8.909 0.003
T-P Interval 0.235 sec 0.367 sec 2.33 0.127
Systolic Blood Pressure 114.5 mmHg 123.1 mmHg 2.91 0.088
Diastolic Blood Pressure 69 mmHg 79 mmHg 0 1
The rates for every student for each of the variables was recorded and averaged as indicated in Table 1. Using the data given, we were able to perform a paired analysis test. The test was performed because this experiment required the same individuals to be used for the before and after results. The average before and after rates were then used in the paired χ2 median test. The results for the chi-squared test are indicated in Table 1.
Discussion
As shown in Table 1, there was a slight change in the before and after values for all the dependent variables. However, this difference was not significant enough to prove that exercise causes and effect on the circulatory and respiratory system. This however did not apply to the P-T interval. The average time value of the P-T interval before exercise was higher than the value after. Since the P-T interval’s P-value was 0.003, which is less than five percent, we rejected the null hypothesis. This also means that there was a higher Chi-squared value. Since the Chi-squared for the P-T interval was considerably high, there was a low probability that the null hypothesis was true. Therefore the before and after exercise values for this interval will be different. This is true according to the literature. The literature states that there should be a decrease in values because of the speed of contractions of the heart will increase with exercise which will cause a decrease in the time interval between the P and T waves.
According to the literature there should be an increase in one’s pulse rate once moderate exercise is performed. This is true because exercise causes a stimulation of the sympathetic nervous system. This stimulation then leads to an increase in the speed at which the SA node is depolarized (Guyton, 1985). However, our data from this experiment did not correspond with the literature. As one can observe from Table 1, there is an increase in pulse rate but since the P-value was 0.2 we had to fail to reject the null. Since the null stated that the rates before and after exercise would be the same, we have to assume that exercise does not have an effect on pulse rate.
Our indicial prediction for the change in systolic and diastolic blood pressure was that there would be a change in values after thirty jumping jacks. According to Table 1, there was a small increase in both the diastolic and systolic blood pressures. Although there was a change in values, our conclusions have to come from the P-value and according to that value we have to fail to reject the null hypothesis. Therefore, we have to conclude that exercise does not have an effect on blood pressure. This conclusion does not match the scientific theory stated in the literature. According to the literature, there should be an increase in values due to the fact that during exercise the working muscles undergo vasodilation while the rest of the body undergoes vasoconstriction (Guyton, 1985). Our data concludes that the muscles and body did not undergo enough vasodilation and vasoconstriction to make a difference in blood pressure.
The T-P interval and pulse lag are known to decrease with exercise but in this experiment our results did not decrease enough in order to reject our null hypothesis. As indicated in Table 1, the P-values for both the T-P interval and pulse lag were greater than five percent therefore we did not have the evidence to reject the null hypotheses for these two variables. Therefore, we had to fail to reject the null which means our experiment did not prove to be correct according to the literature. Both of these values should have decreased because the contractions of the heart quicken. Once these contractions increase in speed, the T-P should decrease because the time between the T and P waves decreased. This also causes the pulse lag to decrease as well. The increase in the speed of heart contractions causes the speed at which a ventricle depolarizes to increase.
According to the literature the T-P interval, P-T interval, and pulse lag should decrease while the pulse rate and blood pressure increase after exercise. Our indicial predictions were that there would be a change in the values. Although we did not specify whether this change will be an increase or decrease, our experiment did not support the literature. The only variable whose data was significant enough to accept our prediction was the P-T interval. Many errors could have caused this discrepancy. One of the main reasons for our results could be based on the type of lead we used. During this experiment we used the lead known as Lead 1. While this is a good and basic lead, there are 11 other different leads available to use (Thaler, 1995). Our results could have been more accurate if we used more than one type of lead. Another error that could have caused our results is the type, amount, and quality of the exercise we performed. An error could have occurred within this factor because not every individual performed this exercise to the best of their ability. Also maybe someone did not perform the correct amount of jumping jacks. Another major reason for the error in our results could come from the time in between exercise and collecting data. Someone could have waited too long after exercise before hooking up the leads to collect their data. This time difference would allow the heart to return to its resting state. This would lead to invalid results. Future investigations of this experiment should include many changes. Some of those changes should be the type of lead, the numbers of leads, and the type of exercise. Next time the exercise should be more intense so that it causes more dramatic changes in the values of the variables. Also someone should determine the quality of the exercise that is performed to insure that valid data is can be collected.