Does Exercise Intensity affect Blood Pressure?

 

Jeff Mills, Becka Ormsbee, Sarah Perzow

 

CU-Boulder, Fall 2007

 

The problem of how exercise affects blood pressure is important for research because it can further our understanding of cardiovascular disease, and overall health. Anyone who has ever done any physical exercise knows that exercise increases the demand on the heart. Our group wanted to test specifically if exercise had a significant influence on systolic blood pressure (sBP), diastolic blood pressure (dBP), and mean arterial pressure (MAP).  SBP is when blood empties from the heart into the blood vessels.  DBP is measured when blood returns to fill the heart.  MAP is the average pressure responsible for driving blood forward into the tissues through the cardiac cycle.  We determined MAP with the equation MAP=dBP+1/3(sBP-dBP).  We hypothesized that as exercise demands increase, the workload of the heart will increase.

To test our hypothesis we designed an experiment that would test the BP values of our participants against a set increase in exercise intensity. We used a stationary bike, and a digital sphygmomanometer to measure BP values. Our three subjects had their sBP and dBP measured after three minutes of pedaling at level five on the bike, after 3 minutes at level 10, and after 3 minutes at level 15.  As a controlled variable, we made sure that each participant did not stop between levels, so heart rate and BP was not affected by a sudden stop in exercise.  Each participant was also tested at the same levels, pedaling between 60 and 70 RPMÕs, so exercise intensity remained the same for each subject for the same amount of time at each level.  As an experimental control, we tested each subject at rest. Before testing our hypothesis, we predicted that our data would show an increase in sBP, dBP, and MAP along with the increase in exercise.

         Our results demonstrated a consistent increase of sBP, dBP, and MAP with the increasing levels of exercise. We ran regressions on the sBP, dBP, and MAP values we measured.  For sBP, the significance of F was 0.000790671; for dBP, F=0.01686628; and for MAP, F= 0.007844869.  Because the F values we found for all three regression tests are below the critical value of 0.05, the relationship between exercise and blood pressure is significant. 

          Our results were consistent our hypothesis that as exercise demands increase, the workload of the heart, or blood pressure, will also increase because our results showed a significant relationship between exercise intensity and blood pressure.  Although our data supported our hypothesis, this experiment could be improved by using a larger sample size.  We also were unable to measure the levels of intensity on the stationary bike in units, like watts.  To control the level of intensity more effectively we would use a stationary bike that can be set to watt levels, rather than just using level 5, 10, and 15. 

         There were a number of experiments on the CABLE web page that tested other factorsÕ influence on BP, such as music and stressful visual stimuli.  In both tests, Wang et al. 2006 and Krohn et al. 2006, the results showed an increase in blood pressure with louder music and more stressful visual images.  Our experiment could be taken even further and be applied to current health studies to determine the intensity of exercise required to significantly lower resting blood pressure in individuals with dangerously high blood pressure, as well as the importance of regular exercise for overall cardiovascular health.