When it comes to cardio, which type is best? The simple answer is: whichever you prefer most. The more complex answer is that it depends on your goals, diet, and training level. Let’s start by breaking down the two types so we can make it a little more sense of it all.

A good way to tell the difference is by using the “Talk Test”. The more intense an exercise gets, the harder it is to breathe—and thus, talk. If you’re exercising and can hold a full conversation with someone, then you’re at the lower end of aerobic training (think about going on a walk with someone and talking the whole time). The harder it gets to talk, the more anaerobic your training is. It’s important to note, though, that mild/moderate difficulty speaking will still fall within the aerobic threshold – so don’t panic if that happens; but if your goal is to be more aerobic and limit lactic acid buildup (i.e. “burn”), then you want to make sure you can hold a reasonable conversation, even if it’s not full sentences.

For most people, aerobic exercise is going to be the best option. It’s more sustainable and easier to fuel for, since the body naturally prefers fat for energy. As heart rate and breathing picks up, the body gradually decreases its use of fats and increases its use of carbs for immediate energy. The aforementioned “Talk Test” is a great way to assess carb vs. fat usage during activity.

As one may assume, the body has A LOT more fat energy available than carbs, so fueling for aerobic exercise simply consists of following a balanced diet; and, as a result, is easier to manage while in a calorie deficit. Anaerobic exercise, however, primarily uses carbs for energy – of which the body has a limited storage capacity. If this is going to be your primary mode of cardio, it’s important that you prioritize carbs in your diet, especially right before your workout.