Kettlebells are rubber-covered metal weights with handles. These are usually found in the free-weights section of most gyms. This is a great form of cardio workout that can help you burn calories build endurance and also give you a good overall workout. These exercises are becoming increasingly popular nowadays because of its effectiveness. But if you are new to this cardio workout then you need to start under the guidance of a good instructor. This will save you from avoidable injuries. But if you are house bound like most of us right now you can also start on your own.