What is a “BMI”? Literally, it means a person’s Body Mass Index, but it is often considered as a comparing measure such as weight. If a person’s BMI is under 18.5, that person is considered underweight. Normal weight is between 18.5 and 24.9, and overweight is is a BMI of 25-29.9. Beyond that, obesity is a BMI of 30 or higher.The components used in order to calculate one’s BMI are the person’s weight and height. Our group’s experiment tests whether one’s BMI affects the increase or decrease in blood pressure, heart rate, and respiration rate after exercise. We predicted that a higher body mass index will result in a higher blood pressure, heart rate, and respiration rate after exercise because the heart will have to work harder to circulate the extra oxygen needed from the extra work load. Because of this heavy work load on the heart, we also wanted to see whether there was a possible correlation between higher BMI’s and probability of heart disease. In the heart attack video we saw in class, the victim was unfit from a poor diet, and experienced a heart attack after exercising beyond his heart’s capability. The independent variables are the BMI’s of the test subjects, and the dependent variables are the change in blood pressure, heart rate, and respiration rate after exercise. We measured these using the Vernier blood pressure and vernier respiration monitor.
In our experiment, we used the Vernier Lab Pro to connect a Vernier Blood Pressure Sensor and a Vernier Respiration Monitor into a laptop. We took four test subjects of different body mass indexes, and took a control for each, measuring their normal heart rate, blood pressure, and respiration rate. We had each subject sprint for 30 seconds, and measured their heart rate, blood pressure, and respiration rate immediately after. For example, subject #1 had a BMI of 21.5 had a 117/62 mmHg blood pressure, a 114 bpm heart rate, and breathed 10.54 breaths per minute. After exercise, the subject’s blood pressure increased to 134/70 mmHg, heart rate increased to 157 bpm, and respiration rate increased to 23.36 breaths per minute. After recording the data for all four subjects, we ran statistics on the increases or decreases from normal blood pressure, heart rate, and respiration rate to the numbers after exercise. We analyzed the data in three different ways for the best expression of the results. We first made a graph comparing BMI with a ratio of the results. The ratio was made by dividing the after exercise number with the before exercise number. For example, subject #1’s ratio in heart rate would be 157/114 which is 1.38, and we compared that with his BMI. The second way we analyzed the data was by comparing the BMI with the difference between the after exercise number and the before exercise number. The last way we analyzed the data was by comparing the BMI with the percent change in blood pressure, heart rate, and respiration rate. As seen in the graph below of BMI vs. ratio of change in blood pressure, there is a clear trend. The subjects with a higher BMI had an bigger increase in systolic, but a smaller increase in diastolic. The clear trend is shown when we calculated the correlation. The graph for systolic blood pressure had a correlation of 0.890, while the graph for diastolic blood pressure had a correlation of -0.726, all figures very close to an absolute value of 1.
Pearson’s product-moment constant of correlation
Correlation is a constant measuring the statistical connection between two groups of data.
Our project provides further insight into the circulatory system. Although the blood pressure, heart rate, and respiration rate increased after exercise as expected, we incorrectly predicted the effects of BMI on heart rate and blood pressure. If a person has high muscle mass compared to body size, BMI will increase. Therefore, the ratio of change for heart rate should be less because the heart and muscles are strong enough to pump the blood all across the body. Also, we were correct in believing both systolic and diastolic pressure would both increase after exercise. However, a larger BMI will cause systolic to increase at a higher rate and cause diastolic to increase at a lesser rate. This phenomenon can be explained by looking at the effects of exercise on the circulatory system. When a person undergoes exercise (in our case, sprinting) their body needs extra oxygen to be able to produce enough ATP to sustain the heightened level of energy usage. Therefore, blood is pumped faster through blood vessels, increasing systolic blood pressure. On the other hand. On the other hand, when systolic pressure increases, the blood vessels are temporarily stretched, allowing the blood to flow more freely through and decreasing diastolic pressure. The stronger the heart, the more drastic the change in systolic and diastolic pressure.
