To most people, exercise is so general a concept that they often consider it to be almost anything, such as walking the dog, weeding the garden, going to the lake for a boat ride, playing a set of tennis, or fishing. Obviously, many people confuse proper exercise with recreational activities.

Exercise, however, is not so general, but very specific, it requires intense effort – but it results in physiologic adjustments or adaptations that make for an improvement in your body's strength, endurance, flexibility, and leanness that will contribute to any skill, sport, vocation, or recreation. Recreation, while it can be demanding physically, typically is not, with the result that there is seldom – if ever – any pronounced change or improvement in one’s level of total fitness. Again, to quote Dr. Darden:

Once the differences between exercise and recreation were unraveled, Nautilus Sports/Medical Industries went several steps further by designing exercise machines that provided the highest quality resistance. That’s why Nautilus provides the most demanding, but also the most productive form of exercise.