There is a peak duty rating with a continuous duty rating. The peak rating is the motor's absolute maxiumum horsepower that it can put out. That makes this rating almost irrelevent for the average treadmill user. Most people will never use their treadmill at maxium speed for extended periods. The Continuous Duty rating is the amount of horsepower that the motor puts out with a continuous load placed on it. This is a much more accurate and relevant rating for the average treadmill user. It tells you how much horsepower is available to you for the majority of your usage application. That is to say that a 3HP continuous motor is able to generate that amount of power not just at its maxiumum, but somewhere in the middle of its power output range. A 3HP peak rated motor can only give you that power when you force it to its absolute maximum, the majority of the time when you use it, it will be putting out much less than 3HP. Therefore the 3HP continuous rated motor is simply a more powerful motor than the 3HP peak rated motor.