Winter swimming improved general well-being among participants in a study conducted by researchers at the University of Oulu in Finland and published in the International Journal of Circumpolar Health (2004; 63 , 140–4).
Subjects completed questionnaires designed to reveal mood states and subjective feelings. At baseline, swimmers and control participants showed no significant differences. After 4 months of swimming between October and January, the tests were repeated. Compared with controls, the swimmers felt more energetic, active and brisk and had significantly higher vigor-activity scores. In addition to experiencing these feelings of well-being, swimmers who suffered from rheumatism, fibromyalgia or asthma all reported pain relief.