Whether it's cardio kickboxing or step, an exercise class can be an incredibly vigorous and satisfying workout where it feels like you have your own personal trainer urging you on. Or it can be boring, embarrassing, or mystifying, with too much meditation and explanation. If you are looking for an exercise class that burns the maximum amount of calories in the given amount of time, two main questions to ask are: Does the instructor keep you moving as much as possible? Can you keep up? If you observe or try out a class, make sure that the activity level is where you want it to be - hopefully out of breath and sweating by the end. Avoid classes where the instructor talks too much or takes up too much class time with demonstrations. In a rigorous class, you can always take breaks when you need them, but forced breaks are rarely fun. Find a class with a difficulty level that is adjustable over time - if you use weights in the class, you'll eventually be able to increase them as you get stronger. There are also moves like the side plank or pushups that have varying degrees of difficulty that you can incorporate into your workout as you improve. If you're a beginner, avoid classes that are too choreography-intensive. You can't get a good workout if you can't do the moves. Find a class where the instructor does the workout with you, making it easy to follow and providing an example of good form. Finally, just look for an active and entertaining class where the instructor mixes it up every now and then so that your body doesn't get too used to the workout.