When it is too cold to exercise outside, try doing it in a pool heated by nature.

About 100 women on Sunday gave an outdoor yoga performance in temperatures of minus 4 deg C at a hot spring in Luoyang, Henan province, as part of a local hot spring yoga cultural festival.

China's Henan province is well known for its many geothermal springs.

They are used for many purposes, including in greenhouses and for general heating, and are thought to have medical benefits.

Geothermal activity deep underground heats the water up to temperatures of 40 deg C to 60 deg C.

Many hotels and health resorts there have their own hot spring wells, which provide mineral water and bathing pools for guests.