I have heard that Headstand Pushups are not part of the Foundation Series. I wanted to ask why that is since they seem to be such a staple exercise.
Also, is this one of those things that isn't in the Foundation Series but once you actually go through Foundation lo-and-behold! you've developed the strength to do them anyways? If so, which series are these muscles developed under? Hollow Back Press? Handstand One?
Thanks.