The psoas muscle is targeted in the (very potentially pseudoscientific) trauma release therapy/exercises thing created by Peter Levine
One of the specific treatment/exercise things he pushes is that you eventually lie down and your legs start shaking involuntarily
But I tried it - followed a YT vid along for like 30 mins and did everything exactly as told - and it didn't work. Couldn't get my legs to shake involuntarily
https://archive.4plebs.org/pol/thread/267174265/