How to give an avatar morphing that responds to movement

I know, I know this is a question that’s more suited to other outside programs than Unreal, but this is a very spacious and friendly place, and I’m hoping someone can help me

I’m talking about reactive morphing and realistic muscle movements, such as when the avatar is stretched, the armpits and back muscles are lifted or squatted, and the back of the thigh is pressed

In the meantime, Unreal Engine has changed a lot, and I’ve been looking forward to seeing if there’s an answer to my needs in a place I didn’t even think about because i don’t really know about rigging to try