When the Arabs invaded Persia around 637 CE, the zourkhanehs served as secret meeting places where knights would train and keep alive a spirit of solidarity and patriotism. Invaders
repeatedly targeted the houses of strength to discourage rebels, but new ones would always be organized in a different location. Following the spread of Shia Islam, and particularly
after the development of Sufism in the 8th century, varzesh-e pahlavani absorbed philosophical and spiritual components from it. Religious hymns were incorporated into training, and
the first Shi'ite imam Ali was adopted as the zourkhaneh patron.
Following the Iranian Revolution of 1979 the tradition lost some of its popularity as the new regime discouraged anything tied to pre-Islamic paganism, which included the Gnostic and Mithraic chants and rituals of the zourkhaneh. This did not last, however, as the Islamic Republic eventually promoted varzesh-e bastani as a symbol of Iranian pride and culture. Today, varzesh-e pahlevani is touted as the reason why Iranians are regular winners at international wrestling and weight-lifting events.
(source citation en.wikipedia.org )