steam. Combustibles on, or near the stove have been known to cause fires. Contact lenses dry out in the heat. Jewelry or anything metallic, including glasses, will get hot in the sauna and can cause discomfort or burning. The temperature on different parts of the body can be adjusted by shielding one's body with a towel. Shielding the face with a towel has been found to reduce the perception of heat. Some may wish to put an additional towel or a special cap over the head to avoid dryness. Few people can sit directly in front of the stove without feeling too hot from the radiant heat, but this may not be reflected in their overall body temperature. As the person's body is often the coolest object in a sauna room, steam will condense into water on the skin; this can be confused with perspiration. Cooling down by immersing oneself in water (in a shower, lake or pool) is a part of the sauna cycle and is as important as the heating. However, it is advisable that healthy people and heart patients alike should take some precautions if plunging into very cold water straight after coming from the hot room, as the rapid cooling of the body produces considerable circulatory stress. It is considered good practice to take a few moments after exiting a sauna before entering a cold plunge, and to enter a plunge pool or a lake by stepping into it gradually, rather than immediately immersing oneself fully. In summer, a session is often started with a cool shower. In some countries the closest and most convenient access to a sauna is at a gymnasium. Some public pools, major sports centres and resorts also contain a sauna. Therapeutic sauna sessions are often carried out in conjunction with physiotherapy or hydrotherapy; these are gentle exercises that do not exacerbate symptoms. Health effects There has been widespread research into the health benefits and risks that come from sauna usage; most studies have focused on the Finnish sauna specifically. Sauna bathing leads to mild heat stress, which activates heat shock proteins responsible for repairing misfolded proteins, promoting longevity as well as protection against muscle atrophy and chronic illness. There is significant evidence that lifelong exposure to sauna (once a week or more) reduces the risk of sudden cardiac death; and that risk reduction is correlated with duration and frequency of use;