Taking a hot bath lowers blood pressure (body loses heat by dilating blood vessels at the surface of the skin, causign a drop in overall resistance to blood flow and so a fall in pressure).
Very hot water is less relaxing. In 15 mins in water at 43C body temperature increases by a degree or two, and pulse rises from 75 beats per minute up to around 115 beats. Return to normal temperature takes about half an hour.
Warm baths aid recovery from exercise by relaxation and improved circulation. The latter aids the dispersal of lactic acid, the end product of anaerobic exercise, and may help to remove fluid that seeps into tired muscles from blood vessels during exercise, and in so doing, helps alleviate aches and pains.
The most soothing temperature is 38C (100F).
Sudden exposure to cold water causes a rise in blood pressure and may stop the heart. Cold showers seem to create a mild feeling of euphoria.
Dangers: Fainting in hot water because of diversion of blood to skin. Heatstroke in a very hot bath if room so steamy that sweat cannot evaporate to cool the skin. A body temperature of 42C to 43C can be fatal.
Source unknown, date not recorded
