Emily McHenry
Human Performance Lab
Methods

For the first part of this lab, we used an EKG to graph our hearts electrical activity. We connected
three electrodes to our subject’s arms and used a computer to create the graphs. We first
graphed our subject’s resting/normal heart rate. We used this graph to record the P-R interval,
QRS interval, QT interval, and heart rate (beats/min) over three trials to average the results. We
then asked our subject to perform an exercise to raise his heart rate; in this case our subject did
pushups for two minutes until he was winded. We then recorded the same information as
described previously again. Finally, we were asked to create our own experiment. For our
experiment, we hypothesized that his heart rate would increase if he held his breath. Our subject
held his breath as long as he could, and we collected the data.

For the second part of the lab, we use an oxygen gas sensor and a computer to determine
residual oxygen levels in exhaled air as well as the percentage of oxygen in the air. We
determined the amount of oxygen in the air and then asked our subject to hold his breath as long
as he could. When he could no longer hold his breath, he exhaled into a plastic bag and placed it
over the sensor. We then collected the data of the percentage of oxygen in his exhaled air. Next,
we collected the same data after having our subject hyperventilate for 10 breaths and then
blowing his eleventh breath into the plastic bag. Lastly, we again were asked to create an
experiment. We hypothesized that the amount of oxygen used in a deep breath would be less
than that in a normal breath because more oxygen was inhaled with a deep breath but in both
cases the time the breath was held remained the same. We simply had our subject take a normal
breath and exhale into the bag then collected data. Next, he took a deep breath, held it for the
same amount of time, and exhaled into the bag to collect data.
Results

For experiment 1, we determined that our subject had normal intervals of voltage vs. times
shown in his EKG. We found the following data: his P-R interval was .13s, QRS interval was .062s,
Q-T interval was .29s, and his heart rate was 60 beats per minute. After exercising, his P-R
interval was .11s, his QRS interval was .06, and his Q-T interval was .24s with a heart rate of 92
beats per minute. After holding his breath, his heart rate went from 60 beats per minute to 98.3
beats per minute.

For experiment 2, our subject held his breath for 149 seconds for the “normal” experiment. The
maximum oxygen in the air was 18.96% and the amount of oxygen in his exhale was 5.96% for a
change of 13.0% oxygen. When he hyperventilated, he held his breath for 128 seconds. The
maximum oxygen in the air was 19.15% and the amount of oxygen in his exhale was 5.30% for a
change of 13.85% oxygen. For the experiment, the amount of oxygen in the air was 19.27%. The
percentage of air absorbed in a normal breath was 5.04% and the amount absorbed in a deep
breath was 3.70% oxygen.
Discussion

For experiment 1, the results were exactly as we had suspected. Our subject had normal EKG
intervals and after doing cardio exercise, he could physically feel his heart rate increasing as we
all have felt before. This reflected in his EKG results because his heart rate had increased 32 beats
per minute and his voltage intervals decreased because his heart was beating faster. For our
experiment, our hypothesis was also proven correct. Since he was depleting the oxygen in his
lungs, his heart needed to beat faster to better distribute the abnormally low amount of oxygen
being absorbed. His heart rate increasing was also a result of his body trying to absorb more
oxygen out of the air.

For experiment 2, based on the results we found that the amount of oxygen absorbed after our
subject had hyperventilated was slightly higher than the amount of absorbed when he was
breathing normally. He was not able to hold his breath longer either. Although he only absorbed
slightly more oxygen after hyperventilating, the difference in time he held his breath was much
less so altogether he was basically absorbing much more oxygen than when he breathed
normally. These results make sense because you feel lightheaded after you hyperventilate.
Although you are inhaling several times, you are also exhaling faster than your body can absorb
the oxygen being inhaled. He absorbed more oxygen during hyperventilation because his body
was starving for oxygen although he had just gone on a jog. Our hypothesis was also proven
correct for our experiment. The amount of oxygen absorbed from a deep breath was 1.35% less
than a normal breath because the amount of oxygen inhaled was increased but the time it was in
the lungs remained the same. Higher levels of carbon dioxide detected in the blood causes our
bodies to force us to breathe because it changes the pH of the cerebrospinal fluid we use to
determine when to breathe.