Temperature extremes include the use of sauna, ice bath and cold water swimming. There are a lot of similarities with sauna and ice baths. They both produce “heat shock proteins” which serve to protect your proteins. Both increase measured levels in the body of Human growth hormone. This hallowed hormone is sometimes called the hormone of youth as it decreases with age and is largely involved in the aging process. It encourages cells to divide.  All cells in the body die and are replaced, except for brain cells but they are another story. As HGH declines, cells don’t replace themselves as often, so any damage tends to stay, which is very evident for example in visibly aging skin.