Conclusions

Two months of aerobic exercise resulted in positive changes as shown by resting heart rate and resting blood pressure results.

Results of the Harvard Step test were mixed.  Subject #1 showed slight improvement.  However, subject #2, who had exercised harder and more often during the two months and showed significant improvement in the resting blood pressure readings actually showed a decline in aerobic conditioning as measured by the step test.  Also, subject #4, one of the controls, showed a decline according to the step test.

I believe the step test has too many variables that cannot be properly controlled.  Even though a metronome was used to try and keep the subjects stepping at the correct rate, they did not always follow it.  The step test is also very difficult.  The 45 cm step specified made it so difficult that subject #1 could not go the entire five minutes and one additional subject dropped out before starting rather than take the test.

I believe a variation of the step test with a lower step and a longer step time might work better.  That way the test would not be so unpleasant and could be repeated more often.  Taking the test weekly would provide more samples and make the results more accurate.  Also if the step test was not so difficult, more volunteers might be found.

Of particular note is subject #2, who was found to have a resting blood pressure (141/92) in the danger zone at the beginning of the testing period.  This reading is believed to be accurate because the subject continued taking pressure readings on his own throughout the testing period and the early readings were all in the same range. 

In researching high-blood pressure or "hypertension" I found that the first number, the systolic pressure, should be below 120 and the second number, the diastolic pressure, should be below 80.  The systolic pressure is the pressure just after the heart has contracted and pumped out blood.   The diastolic pressure is the pressure during relaxation and dilation of the ventricles of the heart while they fill with blood.

Systolic pressures of 120-139 or diastolic pressures of 80-89 are considered to be "pre-hypertension", while systolic pressures of 140-159 or diastolic pressures of 90-99 are considered to be "stage 1 hypertension".  Systolic pressures greater than 159, or diastolic pressures greater than 100 are considered to be "stage 2 hypertension".

Doctors have traditionally focused on keeping the diastolic pressure within the "safe range", as it is the resting pressure and is always a factor.

Hypertension is harmful to both the heart and the arteries.  It causes the heart to work harder than necessary and can lead to heart-attacks.  It is harmful to the arteries and can contribute to atherosclerosis, or "hardening of the arteries".

By the end of the two month period subject #2 was consistently observing readings comparable to the final score measured by me of 116/71, which was within the normal range.  During this period, his resting pulse also went from 65 to 58.  These results were achieved without medication.

Blood pressure for subject #1 remained about the same at the end of the test period, but this would not be unexpected as the pressure was always in the "normal range". 

The results for this project would have been more meaningful if many more people could have been involved, but that was not practical for a 7th grade science project.