High intensity interval training (H.I.I.T) and low intensity steady state (L.I.S.S) exercise are the two most common terms used in the fitness world when explaining the type of cardio someone is doing. People want to debate that one is better than the other, because there are some significant differences between the two types of cardio workouts and why they both have their place in fitness and overall health.
Conceptually, how are they different?
LISS is when someone exercises at a low intensity for an extended period of time where your heart rate stays at a 60-70% max (or you are able to keep a conversation going). This is usually for a minimum time of 30 minutes and is done with full body movements like walking, jogging, swimming or biking. LISS also works your aerobic system, or your systems that require you to use oxygen. It is often associated with the ‘fat burning zone’ because it used more fat calories for energy than carbohydrate calories.
HIIT is when someone exercises at a high intensity in short bursts directly followed by a recovery period or active recovery. True HIIT workouts do not last for more than 15-20 minutes because you are meant to work as hard as you can in the high intensity bursts. Unlike LISS, HIIT is normally done in a circuit style and can be done with bodyweight exercises or weights and accessory training items. HIIT works the anaerobic systems, or the systems that do not use oxygen, and typically you are working at a heart rate of 70-90% max.
What about calories?
This is usually the big question when looking at HIIT vs LISS. People usually think that the latter has more calorie burning, because of the fact that you are exercising longer. However, there is a process that needs to be taken into consideration if you are looking for more calorie burning.
Let’s consider a scenario where you exercise for 60 minutes during a LISS workout and you burn 450 calories. Then the next day you work out for 20 minutes during a HIIT workout and you burn 200 calories. Which day did you lose more calories?
You are probably tempted to say the day of the 60 minute workout, however, that is most likely not true. There is a component of cardiovascular exercise that many people do not know about and it can significantly change the amount of calories someone loses the day of a workout. EPOC, or post exercise oxygen consumption, is a process in which the body consumes a significant amount of oxygen after exercise if the intensity is high enough. This process also causes the body to consume more calories to put the body back to equilibrium by consuming more oxygen. So, with the LISS workout, it is not at a high enough intensity to cause EPOC to occur. However, the HIIT workout will cause EPOC to occur. Because of the intensity, EPOC can occur for up to 12 hours after you completed the workout and burn up to 50 calories/hour to try and return to body to equilibrium. So, you could burn up to an additional 600 calories on the day you completed the HIIT workout.
What about health components? Which is better?
Cardiovascular health: When it comes to this health component, LISS is the best option to improve CV health. The long steady state exercise assists in improving the endurance of the heart muscle, allowing for it to strengthen!
Weight loss and body composition health: HIIT takes the wining spot for this component. The reasoning being that you are able to preserve muscle mass and does not require as many sessions per week as LISS. However, something important to mention is that if someone is just starting out in an exercise program or is returning from a long break, LISS may be an option to start with before moving to HIIT training.
However…
Something important to remember is that you should do things that you enjoy. If you don’t like HIIT training and prefer LISS in forms of hikes, do the hiking instead. If you prefer HIIT circuits over LISS, do HIIT. The important thing is to do exercise styles that you enjoy and you are more willing to do rather than force yourself to get through something you hate.
However, each type of training has it’s pros and cons, so if you can incorporate both styles into your regiment, you will be able to find ways to get both benefits.