This is a very popular topic in fitness when it comes to cardiovascular workouts. Most people ask me which form of cardio will yield the best results. Before I jump to my recommendation, I would like to outline the pros and cons of each style.
First off, let’s start with Steady State Cardio. This is probably the most popular form of cardiovascular activity. In steady state cardio, your perceived exertion is low to moderate difficulty over a period of at least 30 minutes. Examples of steady state cardio are running/walking/jogging on a treadmill without stopping, running a marathon, hiking, etc. Your heart rate is usually 55-70% of your Projected Heart Rate Max over the duration of your activity. While performing steady state exercise, you are working your slow-twitch muscle fibers which are involved in endurance activities and they do not tend to hypertrophy (grow) as much as your other muscle fibers. While the calories you burn doing steady state are mostly from fat, you will not burn as many calories as you would doing interval training for the same period of time. Steady State cardio does not elevate your metabolism post-exercise as well as interval training but is much easier on your joints. People of all ages are most likely to be able to perform steady state cardio consistently without much discomfort.
Next is High Intensity Interval Training (HIIT). HIIT is growing in its popularity due to shorter workout times. Most HIIT workouts last 20-30 minutes and are characterized by bursts of maximum activity followed by a short rest period before repeating the activity. Your perceived exertion is high during HIIT with your heart rate falling between 70-85% of your Projected Heart Rate Max. The most popular example of HIIT is running sprints. During HIIT, you are working the more powerful, more strength oriented type 2 muscle fibers which are more likely to hypertrophy (grow). Even though the percentage of the calories you burn during HIIT that come from fat is low, you will still end up burning more fat during your workout than a steady state cardio session of the same duration. You can also burn up to 100 more calories in the 24 hours following your HIIT workout. There are some things to watch out for with HIIT. For instance, you should not do HIIT more than 3 times per week as it is very taxing on your joints and nervous system. In addition to that, you are more likely to injure yourself if you did not properly warm up before performing HIIT since your muscles are pushed harder than in steady state cardio. It may also be more difficult for older adults to do HIIT since their joints are not as strong as they once were.
After reviewing the pros and cons of both HIIT and Steady State cardio, I recommend that people should perform 2 days per week of HIIT cardio and 3-4 days a week of Steady State cardio to get the maximum health and fat burning benefit while preventing your body from breaking down from over working it. Your nervous system is often overlooked with people start a HIIT program and end up burning out early due to doing too many HIIT sessions.