After getting out of a long, hot shower in which I simply stood, and moved around a little, I had difficulty breathing and felt dizzy; I noticed red on my ankles and what looks almost like bruises on both ankles.
I took my blood pressure, which was 104/63, and my heart rate, which was 121, not long after coming out (and without doing any strenuous exercise).
Now I understand why I might get so tired after coming out of the shower.
EDIT: After relaxing, lying down, for about 10 minutes or so, my BP is now 98/67 and HR is now 72, a near 50 point drop!
EDIT 2: Note that I enjoy long, hot showers and often think about topics of interest while I'm in there.
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"You have a responsibility to consider all sides of a problem and a responsibility to make a judgment and a responsibility to care for all involved." --Ian Danskin