This is so simple and easy to do that you have no excuse not to do it. In his phenomenal book "Anatomy Trains," Thomas Myers describes various fascial trains that connect the body. The one of particular importance to most people is the superficial back line, which runs from the bottom of the foot to the top of your skull along the backside of your body (calves, glutes, erectors, etc.).

Your plantar fascia runs along the bottom of your feet and is tightened by limited ankle mobility, tight calves/peroneals, and just overall daily stress. For most people, just their feet will hurt, but for many, the rest of their posterior muscles will be locked up as well. Grab a tennis or lacrosse ball and roll on it while you're sitting in your chair at the office. In doing so, you'll help loosen up the plantar fascia underneath your feet and provide a "systemic release" for the rest of the body as well.