Four miles in 28 minutes: Wednesday, June 5th, on treadmill.
Four miles at 1% grade: Done today, on treadmill, in under 32 minutes.
On Saturday I ran the big loop again in the park with Justin and Ezer, My time was right at 52 minutes, which is a full minute slower than my best time; then again, it was considerably warmer and very humid Saturday morning.
The last half-mile or so, leading up the hill to the corner of Central Park West and 110th Street, I really started pushing myself. Within 100 meters of the end, however, I started feeling chest tightness that radiated to the neck and nausea! The sensation stopped nearly immediately once I slowed my pace.
I know what exercising at 15-16 METS feels like, and I believe I was doing considerably more than that, given the grade of the hill and my speed. But still, the experience brought about a good deal of existential clarification when it comes to the concept of angina. I suspected that I was feeling a demand ischemia.
I mentioned this experience to one of the ICU Anesthesiologists, who scoffed at the idea that the pain was cardiac in origin. He mentioned chest wall tightness. I'm doubtful. Theoretically, if the heart rate were not limited by intrinisic properties, someone young like me might push his heart rate to the point where the organ demands more oxygen than can be delivered. This doesn't mean I have coronary artery disease. Just a heart that can beat faster, perhaps, than it should.
It's hard to imagine someone feeling the sensation I felt (but sustained and not relieved by rest) and not take himself immediately to the hospital! Scary!
And if you work for Aetna and happen to be reading this, my identity is obscured for a reason!
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4 comments:
What is "METS"? Will you please explain what your fourth and fifth paragrams mean in simple English??
METs is short for "Metabolic equivalents." (I know, I know, even with the internet and powerful google searches, this information can still be quite difficult to find.) It's a measure of metabolism, or oxygen use. Walking an easy pace is about 4 METs. Playing doubles tennis is more like 9 or 10.
"Demand ischemia"--we'll break this down. Ischemia means that body tissue is not supplied enough blood or oxygen. Usually this is due to coronary artery disease (blockages in the arteries), but the difference with "demand ischemia" is that there's no blockage, just an exceedingly high requirement for blood or oxygen. Because that demand may not be met even with normal coronary arteries, ischemia results, which means pain. (This pain I experienced, by the way, felt very different from being "lung tired," i.e., tired and short of breath.)
This explanation should make the fifth paragraph more clear.
So in extreme cases of demand ischemia, could you have a heart attack?
Is "chest wall tightness" the same as "lung tired"?
And *how* do you know what 15 - 16 METs feels like?
I should clarify--people with coronary artery disease can still get "demand ischemia." Doesn't mean they're having a heart attach; it's just when the heart isn't getting enough oxygen for the rate it's pumping at.
First question--the body is full of wonderful negative feedback cycles. A heart attack happens when the heart muscle suffers permanent damage (i.e., part of it dies) owing to lack of oxygen. This takes many minutes to happen. When I experienced the pain, I slowed down immediately (negative feedback). The pain resolved as soon as I rested, which means with rest, the heart instantly got enough blood again (assuming my theories are correct). So a few seconds of ischemia would be very unlikely to cause permanent damage to the heart muscle.
Second question--I'm really not sure what chest wall tightness feels like, but it would be related to either cramping of the chest wall muscles (the muscles between the ribs) which might happen with electrolyte abnormalities or direct physical injury to the muscle. When I referred to "lung tired", I was thinking of something I read that stated beginning runners (in fact, almost everyone I suppose) is more limited by their lungs than by their hearts. In other words, the heart generally has more reserve for sudden strenuous exercise than do the lungs. So when you sprint up three flights of stairs, you're short of breath but your heart is able to maintain a good blood pressure.
I have a general idea of what 15 METs feels like because the treadmills I often run on have a computer. I enter my weight, and it tells me calories consumed and METs. Changing the pace or changing the incline both affect METs.
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