Before revision: Mudras were thought to block the central sushumna nadi channel and work to force the flow back up, or in the case of Viparita Karani actually reverse the flow, using gravity.
After revision: of the subtle bodyMudras were thought to block the central sushumna nadi channel and work to force the flow back up, or in the case of Viparita Karani actually reverse the flow, using gravity.