Zone Training for better results. Some HR ranges are better for weight loss or cardio conditioning than others. Past a certain level (lactic threshold), you will only last so long before bonking, so by using a HR monitor you can make sure you don't exceed that upper limit if you still have a lot of distance left on your ride. That helps me because I can easily be goaded into exceeding my LT and burning up my reserves when I shouldn't and paying for it later.