If you're a beginner, then use the exercise bike for a minimum of 10 to 20 minutes. Do this for a week or until it's comfortable for you. As you get used to paddling or building up strength, slowly increase the timing of your exercise up to 30 minutes per day. So, after about a week or 12 days, you can add another 3 minutes easier effort and 2 minutes harder interval. This will total up to 30 minutes. Don't exceed this, or you'll end up with sore muscles. Hence, by the time you're working out for 30-minutes, you're achieving the minimum amount of exercise per day.