The underwater traction therapy is a passive procedure designed in the 1950s by Dr Károly Moll, a Hungarian rheumatologist. It spread from Hungary to neighbouring Slovakia and is favoured in world-renowned spas like Hévíz and Piešťany. It can be performed in normal lukewarm water as well; the effect is comparable to that of traction in mineral thermal water. The content of the minerals in thermal water makes human bodies float more than in common tap water, therefore somewhat heavier weights are necessary in the mineral water to produce a comparable traction force.