I don’t believe in “biorhythms” except the obvious ones, the days and the seasons, but it is a fact that lately I feel kind of run down, sore and tired and needing more sleep. Which, unfortunately, I tend to deny myself because my best ideas invariably crop up around 11PM.

I meant to take just a short walk, perhaps half an hour on flat terrain. No jogging. Just a leisurely walk. Well, it ended up about one hour and ten minutes. But I did not jog. Rather, I walked over two hills, with long steep slopes. So, uh, basically the same intensity as jogging, but harder on the knees because of the long downhills. -_- It kind of just happened.

Tomorrow I will definitely do better. Or, in this case, less.

I have watched carefully, and I definitely get winded at a lower pulse than before. That is not a good sign, or at least not in itself. The context is kind of puzzling.

Literally overnight, it seems to me, my pulse went down 5-10 beats per minute about a week ago. So it is low even compared to what I was used to, which was pretty low. But this time it is not my resting pulse. It is my working pulse. But the thing is, I still get winded at the same speed and distance as before, even though my pulse is lower at that point. Actually, I seem to get winded slightly easier than before.

This makes a kind of sense, for the oxygen saturation in the blood depends on the function of both lungs and heart. The faster and deeper I breathe, the more oxygen there is in my lungs; and the more blood that flows through the lungs, the more of that oxygen is brought to the body and eventually the brain stem that regulates both the pulse and the breathing. If my lungs work as before, my heart is as strong as before, but beats more slowly, then less blood is going through the lungs and a little less oxygen is carried around. The difference is quite small, since the pulse is less than 10 BPM slower (like 130 instead of 140, for example). But I seem to get winded quicker when jogging and breathe deeper when walking fast.

In contrast to this, I seem to be able to go faster further before my legs get heavy. Early in the month, just after I had learned that I could jog without falling over dead at once, I could jog on the bridges during my first half-hour round (the bridges are from 10-15 minutes from start) but not on my second round (where the bridges are 40-45 minutes from start, obviously). By then my feet were too heavy for jogging. Now, there is no noticeable difference between the first and second round. Of course, I can still only jog short stretches if I don’t want to trigger my asthma, but I can now do this more often for longer. I don’t think that is related to the lower pulse though. It seems to have happened more gradually, and is really what you would expect. If people do something almost every day, their body will adapt to it, within reason. And this exercise is very much within reason.