Baby slamming legs

I have a 5 month old.

About a month ago, shes started slamming her legs down and is doing it constantly. As soon as I lay her down for floor time, in her crib, to change her diaper, in her bouncy chairs, anywhere she does it. She brings her feet up almost to her face and then slams them down onto the ground and does it over and over and over and over again 😅 And she does it with such force as well. I live in an apartment, and if shes doing it on the floor, my neighbours below can here it, so i have to put her on a padded blanket or pillows to muffle the banging noise!

She is happy whilst shes doing it, she smiles and giggles, so i dont think shes doing it in pain or anything.

I’m a first time mom and never seen a baby doing this, is it a normal behaviour??