High Intensity Interval Training (or HIIT) is an increasingly popular form of cardio training for fat loss. But many people still prefer and do quite a bit of steady state cardio, cardio that is done at a constant rate. Is one better than the other? Perhaps a more important question, is one better than the other for you? Can either or both methods help you reach your goals faster?
HIIT cardio in keeping with its name is more intense. You actually burn more calories in a shorter amount of time relative to a typical steady state session. Another benefit of HIIT is that your metabolic rate is elevated to a greater degree post workout for a longer period of time after doing HIIT versus lower intensity work. This is a great thing as it’s not how many calories you burn while training that will make the difference, it’s how many you burn at rest. That will primarily be determined by maximizing your metabolic rate, but the greater post exercise caloric increase is an additional factor.
Steady state cardio is somewhat lower in intensity and done generally for longer time periods. While it doesn’t burn as many calories per minute, the longer you do it, the greater percentage of fat it utilizes for energy versus other options along the energy continuum. If steady state is done after hard resistance training or at a typical low blood sugar time like the morning, (you don’t need to be fasted btw) it will tend to utilize fat for fuel even sooner than if you were starting it on full blood sugar and glycogen reserves.
A typical HIIT session should last between 12-20 minutes. If you’re doing 45 minutes, you may be doing intervals but you’re not doing HIIT. HIIT intervals should be all-out efforts of work, usually 20-45 seconds in length, followed by a recovery (or active recovery) period that’s usually 2-4 times longer than the work period. For example, lets say you do a max sprint for 30 seconds (you won’t be at max speed that whole time but you put in max effort), once that’s over, you should be gasping for breath, trying to recovery your breathing rate as you walk it off. This can take anywhere from 60 seconds to several minutes depending on how hard you worked and what shape you’re in. Think of an elite sprinter trying to do an interview right after a race. They can barely speak. THAT’S what a HIIT interval should feel like. You can do high intensity intervals on an exercise bike, in the pool, on an elliptical machine, on a treadmill (carefully), or even with resistance or bodyweight movements like burpees, tire flips, sled pulls, etc. Anything that you can safely do all-out for a controlled period, then be able to safely rest/recover from being close to spent, can work (but don’t do swimming sprints in the middle of the ocean for example).
A typical steady state session usually starts at a near warm up pace and doesn’t get too much above this. The lower the intensity that’s involved, the more fat is used as fuel relative to other energy options. It’s the duration that is the key and steady state sessions usually start at 20 minutes and go up from there. Personally, I would never recommend doing more than 45 minutes at a time as it can be very muscle wasting but many people go 60-90 minutes or more. One issue with doing steady state cardio is that the body is very adaptive. The more you do of it, the better you get at it. This is great if you’re training to do a marathon, not so good if you’re trying to burn maximum body fat. You simply get so good at doing cardio that you have to go longer and longer to see any appreciable results. It can be effective to switch up the mode or type of cardio you’re doing to slow down how fast you adapt. Also, instead of automatically increasing the length, after you get to a certain point simply increase the pace (go faster or at a higher level or elevation setting, etc.) to keep seeing results.
So which one is best for you? On paper, it would seem that HIIT should be the choice. However, HIIT is definitely more advanced. Also, the intensity involved in HIIT will definitely effect your fatigue level and recovery ability more than steady state, especially if you’re dieting. If you’re also doing a lot of intense resistance training, doing too many HIIT sessions a week can really wipe you out. Steady state sessions may be a very good entry level of cardio for many people or a lower intensity option if you are starting to feel the effects of too much overall work. HIIT can definitely be a time saver in that you are done a lot sooner. But if you haven’t yet adapted to steady state, 20-30 minutes might be all you need, so time may not yet be a factor.
So how do you break it down? If you’re completely new to fitness, start off with some low to moderate intensity steady state cardio. 2-3 sessions of no more than 20 minutes should be plenty. You just want to do enough to cause your body to start/keep moving in the right direction. If your more advanced start with 1-2 HIIT sessions of 12-20 minutes (after warm-up). If you do two sessions try to do them on non-consecutive days. You can do 1-2 HIIT sessions and 1-2 steady state sessions to balance it out. Remember, more is not necessarily better. You are simply trying to stimulate your body to respond, not impress the rest of the world with your dedication. And just a reminder, if you’re diet isn’t right you can’t cardio your way to your best look!
For illustration, my contest prep clients at their peak don’t normally do more than 3 HIIT sessions a week and may do 2 steady state sessions on other days in combination with that for a 5 cardio session total. Those HIIT sessions are typically 20-25 minutes and the work/rest mode will vary based on their body type and metabolic needs. Their steady state sessions will start off at a lower time (20-25 minutes) and increase only 5 minutes a session as needed to maintain progress. Once a max length is reached, if needed I may have them incorporate some intervals halfway through the session to get a better response. I may also add 5-10 minutes of low intensity steady state at the end of a HIIT session to take advantage of the fat burning mode but still control the time frame and energy expenditure. But again, those are high-end techniques for top level physique athletes. The takeaway for you should be to start with a minimal amount and gradually increase as needed. You can overdo HIIT in terms of frequency and length and you can overdo steady state in terms of length or duration.
So, both methods can be a very effective part of your cardio fitness program for fat lose. Give them a shot and see how you respond. They have completely different feels and effects, but can nicely compliment each other to push your toward your goals. Your mood, energy level, available equipment option, environment, current fitness/wellness level, etc., can all effect which one you could/should do on any given day. Listen to your body and see what it tells you both during and after the sessions. Eventually you will find that both HIIT and steady state can be very complimentary cardio tools that you can pull out of your fitness box as needed.
Photo: Terry Goodlad Model: Ramon Ramjit-Munoz