Not at all. The tipping forward one is core strengthening and eventually you would be using similar muscles to hold your horse, to dampen down forward energy , as in the half halt or if you wanted to collect a canter; YOu would drop your knee down, engage your core and lift the front of your chest/belly while becoming firm in the back.
The towel one was one I got out of a Mary Wanlass book. It is to stanbilize the back. She talks a lot about "bearing down", and talks about how we need to be able to have enough muslce town in our body to resist the pull on us that happens when the horse moves forward, we tend to slip back. Most people use the reins to counter act that pulll backward. She says use your core and back. I really don't know the details but it couldnt' help to stabilize the back. While you do this, she says to breathe out powerfully , saying "Pshht". The muscle engagement one feels is what bearing down should feel like.
As for me, I have found that doing Yoga is a great way to cross train, but I am NO athlete. It just helps with learning to breathe slowly, standing very upright and stacking oneself over your hip, knee, foot.