As long as your heart rate is at the target area for fat burning for at least 20 mins then yes, it is a workout.
For my age, if my heart beats around 112 to 125 per minutes for at least 20 mins, I start burning fat. It takes 20 mins to start burning fat..which is why I have fat burning exercises for around 40 to 45 mins after I weight lift during my 90 mins workouts and one hour of fat burning workouts 2 times a week.
