I was working with one of those punching bags with the water in the base trying to find the proper alignments for compression using the resistance of the bag to push against in various shapes. Testing myself by feeling my triceps while pushing, I noticed that no matter how relaxed I started out, at some point my triceps would tense up. If I go on the assumption that there should be no tension in the arms at all at any point then I must be mobilizing that muscle group to push the bag away at that point. I even setup my push so that I was bracing my elbow against my hip so that the upper arm was not required at all and I still tightened up my triceps. I also tried working the alignments with a feeling of receptivity of the bag and also with placing all of my attention in my foot. Both of these approaches yielded better results but I still couldn't keep from tensing up. Is this a sign that I am holding the bag out or pushing it away subtly rather that allowing the weight of the bag to compress down to my feet or is a very small amount of tension in the triceps necessary or inevitable? If I should continue to try and eliminate all tension from my arms, do you have any suggestions for ways I can train to eliminate the tension?
Bags aren't the best training devices for pushes. But to answer your question: fail. Instead of moving the bag and trying to relax the triceps, relax the triceps and try to move the bag. The operative words here are "do" (relax) and "try" (to move). This means that the most likely result will be failure to move, but success at relaxing. Once you've found action in which your muscles are relaxed, then keep that and search for ways to move the bag with relaxed muscles, not with something else. You may not get it in a week or year.