Another variation, especially for tinifying the nervous system is this:
Standing in a hot shower, blast your spinal area and front trunk with hot water as hot as you can stand for about 5 minutes, then turn off the hot and only allow cold water to hit your spine for 30 to 40 seconds. The repeat this hot/cold treatment several times in this session.
*IMPORTANT* Always use a shower filter that removes chlorine (they are inexpensive) because your skin absorbs a very significant amount of water when bathing and showering.