When I'm doing cardio to burn calories and get my heart rate up, I tend to measure my workout by distance. I have mapped my runs so I know the distances. I ride with a bike computer that lets me know my trip distance — very gratifying. When I swim, I like to measure by laps. I used to measure by time, but I find that having a distance in mind is a great goal and it makes me push a little harder.
When doing cardio, you've got to measure your workout somehow so you know when it's complete. So tell me . . .