Yogasthanaka Murti of Vishnu is worshiped by Yogis and all those devotees who have subdued the senses, who have no attachment and those that have quelled all forms of materialist ambitions – those who work without thinking of results and its fruits. It is also the form of Vishnu that should be worshiped by those devotees that are working towards self realization.
Yogasthanaka form of Vishnu has four arms and is dark in color. The back right hand carries chakra (discus), the front right hand is in abhaya or Varada pose. The back left hand holds the conch (Shanka) and the front left hand rests on hip.
Sage Bhrigu and Sage Markandeya is believed to have had darshan of this form of Vishnu. In images they are shown as kneeling down on the left and right of Yogasthanaka Vishnu.
The main murti of Yogasthanaka Vishnu is accompanied by murtis of Shiva and Brahma. Usually the murtis of Shiva and Brahma are found on the walls near to the Yogasthanaka Vishnu.
Yogasthanaka Murti can be found at Mahabhalipuram and numerous other Vishnu temples in Tamil Nadu.
Source - image and information for the article from Elements of Hindu Iconography Part 1