Unless you’re are a fitness professional or a sports geek, chances are, the acronyms HIIT and LISS are foreign to you. HIIT and LISS are today's top fitness trends, the "it" exercises especially if you’re keen on achieving a spornosexual physique—pause and nod for Brad Pitt in the film Fight Club. Right, right?
HIIT (High Intensity Interval Training)
HIIT stands for High Intensity Interval Training. HIIT started off in the 1970’s when an athletics coach named Peter Coe devised sprint and rest sessions for his son who was a runner. It then took off in the '90s through the work of Professor Izumi Tabata with Olympic speedskaters. The resulting Tabata Regimen advocates 20 seconds on insane mode at about 170% VO2max (the measure of the maximum volume of oxygen that an athlete can use or it’s peak oxygen uptake) followed by 10 seconds rest but the whole shebang done repeatedly for 4 minutes. Other last names are involved as well. There’s also the Gibala Regimen that advocates 8 to 12 cycles of 60 seconds of intense exercise at around 90% V02max and 75 seconds of rest. There’s a Timmons Regimen and a Zuniga Regimen as well, each with varied cycles, V02max burst levels, and timed rest periods.
HIIT is also called SIT (Sprint Interval Training) and sprinting basically defines the beat of it. You sprint through short intense anaerobic (your body’s demand for oxygen outstrips its available oxygen supply) workouts interspersed with quick rest or active recovery pauses. HIIT significantly improves cardiovascular health and maximizes your V02max. So net effect, your heart rate gets elevated quickly and produces an after-burner effect wherein you’re still burning fat way after the HIIT session. So it’s perfect for efficiently burning fat and calories in very short amount of time. Like a quickie, in fact.
Balance is Key
There is a caveat though, research notes that the strenuous and admittedly extreme nature of HIIT, not unlike quickies, demands that you be at an extremely high level of motivation. Pause and tip your hats to our animal idol, the jackrabbit. Balance then is key, as jackrabbiting every day may be counterproductive and somewhat perverted if you’re not a professional. So, if you’re a newbie, look at doing HIIT twice a week to start then work your way up progressively to 4 times a week if you are so inclined. Balance that out with LISS training as a recovery or rest day regimen.
LISS (Low Intensity Sustained State)
On the other hand, LISS stands for Low Intensity Sustained State cardio training. If HIIT is a sprint, LISS is like a marathon albeit done luxuriously. Think long, slow, and steady strokes with maybe some Arctic Monkeys playing in the background. In contrast to HIIT, LISS cardio training involves relaxed endurance work like doing: long walks, slow tempo jogging, long steady swims, steady bicycling, or weighted rucking. LISS training has been around for awhile but has seen resurgence through the work of Kayla Itsines, an extremely influential Australian trainer and Instagram celebrity.
In her blog, Kayla cites 4 reasons benefits for pursuing LISS cardio training: 1) It builds fitness levels as it’s easy to do and maintain as it puts minimal strain on the body 2) It’s easy to stick to doing especially if viewed as a recreational activity rather than as a workout 3) It’s great for recovery because of its low impact nature and can actually help increase blood flow for muscle repair and reduce stiffness and 4) Is that it helps burn fat due to the increased oxygen availability at low intensity.
LISS Me or HIIT Me?
So which protocol should we use to achieve our much-wanted physiques? That lean and mean look is achieved primarily through fat loss. LISS cardio training supports fat loss by virtue of fat being the primary fuel source for when we pursue low to medium intensity training. Doing only LISS training though will actually end up in muscle loss over time as your body will look to the muscles as a source of fuel "due to the much lower caloric requirements of burning muscle" according to Jake Peterson, a NASM-certified and Precision Nutrition-certified trainer, in his Popsugar interview. HIIT is actually more efficient for fat loss as it primarily uses carbohydrates as as fuel with fat as a secondary source. This dynamic results in improving cardiovascular respiratory fitness, drastically improved athletic ability, and heightened physical conditioning. And all of those gains are supported by the aforementioned ‘afterburner’ effect.
As fat loss is key, combine both. Chris Martinez of SimplyShredded opines that both protocols possess unique benefits unto themselves and that “they both should be incorporated into your routines since each have specifically different effects.” Have HIIT as your base to burn away fat. Then when you’re not HIIT-ing it, use LISS cardio training to supplement fat loss and support your regimen by acting as an active recovery day. Throw in resistance training as recommended by a professional and pretty soon you’ll be wanting to wear tight slacks and red fur jackets to show off that Fight Club physique.