Activity simply refers to movement, like cleaning the house, walking the dog or throwing the Frisbee. Exercise is purposeful and planned activity designed to obtain health benefits. Exercise includes power-walking, running, aerobics and weight training.
Though you may run while playing Frisbee, or lift heavy objects while working in the yard, the difference between the two activities is the level of intensity. A short burst of running to catch a Frisbee is light effort compared to running at the same pace for three miles straight.
Unfortunately, many people spend a lot of time walking, and very little time exercising. If you want to make sure your walks are exercise, here are 5 Tips to make your workouts more powerful from my latest article, “Do Your Power Walks Lack Power” at Answers.com