Proving the Null Hypothesis – Cardio Version

One of the most under-valued things in science is proving the null hypotheses. The Null Hypothesis states that if you do X, nothing will happen. There will be no reaction, the bacteria won’t respond to the drug, the rat won’t get cancer, the mineral will not fluoresce. Everyone wants their experiment or test to do something, but often proving the null hypothesis is as, if not more, important than making a lab-rat turn plaid and start dancing the hora.

Last, week I decided that I needed to test a null hypothesis, cardiovascular version.

I had noticed that starting in early April, when I walked south into a southwest wind along one stretch of road, my chest tightened and I had trouble keeping my pace steady. I have been tested for cardiac problems in the past and found normal, but things change, and I am somewhat overweight. Fit and strong, but above the “normal” curve at the doc’s office. I also have the (unwanted) ability to work myself into a condition that mimics a heart problem.

One morning, I managed just that. I’d gone walking the evening before without any difficulties, including a long uphill slog at a fast pace. That morning, I turned into the wind and after maybe twenty yards, I had to slow down. My chest felt tight and I was not quite gasping for air but it was not fun. However, my cardiac flow seemed normal, per the finger test.* I guessed that it was the gunk in the air, because although it was 0600, the southwest wind had been blowing all night and the humidity was around fifteen percent.

However, the tightness and comparatively high heart rate did not subside as fast as they usually did. Between that and some other stuff around the house, by the time I was going to Day Job, I managed to work myself into a full-out worry-train of was I having heart problems, I don’t have time to go have another ECG and EKG done, who will cover [other teacher] if I have to have tests, should I tell the nurse, why isn’t my pulse slowing down, who will cover me if I am having a real heart problem and need surgery… Yeah. It took three hours before I came back down to non-freaking-out. Granted, no one around me noticed what was going on, because I’ve gotten pretty good about riding these spells out without scaring people, but it is rough on me to run at Threat Level Reddish-Orange for hours at a time.

What I needed to do was to prove that it was not my heart. The next day after work, I went to the gym. The nice, air-conditioned, and air-filtered gym with two pools that help keep the humidity above bone-dry. I got on a treadmill indoors, set the incline at five percent (close to the long slope where I was having problems) and after warming up, set the pace at three point four miles an hour. When nothing happened, I hiked it to three-point eight MPH and held that pace for as long as my shin-splints would permit, the better part of half an hour. No problems, no chest pain, no shortness of breath, no vertigo, no mysterious headaches, no heart-burn-like feelings, nada. I tried eight degrees and three and a half miles and hour, and no problems. My peak heart rate was 138 beats per minute.

As I walked back to my pick-up, the tightness returned even as my pulse slowed to resting normal. Did I mention that outside it was 84 degrees with a dew-point of 4 and blowing dust?

It’s not my heart. It’s the crud in the air, at least with a southwest and west wind.

But I still need to lose weight.

Follow Up: On Friday I repeated the experiment, but at 15 degree incline and 2.5 MPH. I did OK, but at three MPH and fifteen degrees I was slogging hard, so I backed down to eight degrees and three point eight mph. And no problems. It’s the gunk in the air.

*Press on a finger so it turns white. Release it. If normal color returns in three seconds, no worries. It’s not as good as a real pulse-O2 meter, but it is a decent quick-n-dirty check.