[Lewis Thomson (OP)]

Jon is eager to find the answer to this question.

"When one exercises, among other things, one's core body temperature
often rises, and one's heart rate rises.  Of course, various muscle
groups also are stressed.

Suppose you just sit in a hot tub for an hour.  Your core body
temperature will rise, your heart rate is likely to rise, and you may
well sweat.

Does sitting in that hot tub, which stresses your heart and body, confer
any benefits similar to "real" exercise?  It would seem that it might,
if one puts the "various muscle groups" aside."

Discuss your thoughts in the comments below...

[ryanshah23]

The majority of people's cardiovascular health can be improved by taking a relaxing hot tub session, which will increase heart rate and reduce blood pressure. Hot water immersion may have "robust" effects on blood pressure and vascular function.

[evan_au]

The optimum temperature for sperm production is a bit less than the body's core temperature of 37C.

A hot tub above 37C will impair sperm function.

Note that long immersion in temperatures above 37C can result in heat stroke.