In a recent study, one group of participants watched video recordings of themselves running on treadmills, and a second group watched recordings of other people running on treadmills  When contacted later, participants in the first group reported exercising, on average, 1 hour longer each day than did the other participants
This shows that watching a recording of yourself exercising can motivate you to exercise more
In another study, people who watched recordings of themselves lifting weights exercised for more time each day than did people who watched recordings of themselves running.