HIIT is all about working as hard as you can while being efficient and injury free, so you can consistently continue to train hard and get killer results. Warming up your body before starting your HIIT workout will help increase athletic performance. This cardio warm-up is similar to a general pre-workout warm-up where the main objective is to get your joints mobilized, muscles warm and heart rate foreign, all in preparation to go at it in the workout. Failure to warm-up will increase your risk of sustaining an injury. With that said, some people need to warm up more than others.