These standing poses will wake up the back of the legs.
Give the poses and your legs time. Muscles take a while to increase their length, so, just like you would not expect your muscles to grow immediately (think Pop-eye) don’t expect to be as bendy as Olive oil immediately either.
The stretch should feel more like a wide stretch in the main part of the muscle rather than a sharp pointy stretching sensation at the top of the leg near the buttocks.
Keep each stretch within your own capacity and enjoy the sensation of fresher feeling legs.