An hour and a half of moderate exercise today, starting with indoors biking followed with a brisk trek outdoors. I was kind of inspired to make a tiny bit more effort after reading a popular science article. I may however need more science, and not quite so popular, to find out what happened next.
After I came home, my pulse remained 30-40 beats above normal for about half an hour. The heartbeats were also stronger than normal, so there must have been a lot of blood rushing through the body. However, I was not breathing any different from normal, so it seems it was not oxygen the body was screaming for. What then?
Exercising a bit harder than usual may have used more glycogen compared to fat, so I suppose the muscles and liver may have been busy rebuilding these reserves. However, a glass of sweet juice had no noticeable effect, although it should have caused a spike in blood sugar within a few minutes, sugar which the muscles could have absorbed to build glycogen.
Possibly protein, then. Muscles that are used more than normal will try to add more muscle fiber, and unlike fat and carbs, it doesn’t seem the body has much of a storage shed of unused protein. In all fairness, there is protein in almost all food (not just meat, as Americans seem to believe). Not in juice, though. But in vegetables, milk, egg, even pasta and bread to some degree. After a while I ate some yogurt, and 10-15 minutes after that the heart rate returned to normal. This could be pure coincidence, of course. I need to experiment more with this if I am to find out what causes this.
It is normal for people after hard exercise, like running, to be winded for a while and have a high heart rate until their breath returns to normal. That is not what happened here. I was breathing normally and the heart rate was not near maximum at any time, but it just did not return to much below exercise level for half an hour. So the body must have been doing something.