An abundance of studies have demonstrated the power of touch on everything from Rhesus monkeys to students in a classroom. A pat on the back or a brief touch on the shoulder can express support and reassurance, making the recipient more willing to take risks and improving his decision making. Next time you want to communicate support to a colleague, convey your intention through a small touch. Often times, contact can be more powerful than words. Use touch sparingly though, and don't linger; it only takes a brief moment of contact; any longer can feel creepy.
Source: adapted from "An Effective (and Underused) Way to Reassure and Motivate" by Peter Bregman