Most assuredly. First, it is too complicated to suggest related to ADD or anything else. Consulting medical expertise is best. Regarding how to control 'my rapid' foot movement especially with right leg crossed over left, is simply placing it flat on the floor. I can only do that for so long before my anxiety increases too much. Why . . . not sure, but apparently my doctor does. :)
With writing or sitting for long durations I take a break every 30min. The classes I took for power reading at the university level all stated read / study for 20 - 30 minutes then take a break. That does help.
Also, I realize with myself it is both anxiety and biological as shared by my doc. To combat the anxiety I simply journal before I write. I know sounds counterintuitive. What I journal are what is troubling me. I kinda' get the anxiety issues on the table sort to speak. Then I reread.
Many times that is enough to offer a more calming sensation. Sometimes I explore troublesome issues rather than write a hub. Rest. And, then write the hub later. I find if at awakening I immediately other than drinking water or a short walk roll onto writing the hub with no TV or other subliminal messaging to occur I am much more affective.
Again, I use the 30 min plan and take my breaks of 5min or more. May I suggest some basic research into cognitive-behavior techniques. Essentially that is what the journal process is. It may be all of a few minutes or longer. Empty the automatic negative thoughts. Google that. Also, mindfulness techniques are very, very helpful.