I was terrible at high school science, but I did learn enough about Newton's first law of motion to know that an object at rest tends to stay at rest and an object in motion tends to stay in motion.
Many of you haven't exercised in years. But let me assure you: once you become active again, you will want to continue working out. Activity begets activity. Inactivity begets inactivity. It's really that simple. The scientific term for this is inertia. It's human nature to resist change, but once we get started we don't want to stop.
Where to start? With walking. All you need are shoes!