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HIIT or LISS? What does it all mean?

Buzzwords tend to be prominent in the fitness industry. While sometimes these words and terms are effective and relevant, other times they are simply used for hype. Two common terms remain consistent throughout the cardio-focused aspect of training: High Intensity Interval Training (HIIT) and Low Intensity Steady State (LISS). Before debating which form of training is superior, let’s go over each method and highlight their respective benefits.

High Intensity Interval Training – HIIT

So, what is HIIT?High Intensity Interval Training is a type of training that is defined by short bouts of high intensity exercise broken up by short, intermittent periods of rest/recovery. The high intensity exercise most often takes the form of anaerobic cardiovascular activity, including sprints, battle ropes, ball slams, etc. and lasts a relatively short (typically ≤ 3 minutes) amount of time. HIIT can even be performed with resistance training. Just remember, when performing HIIT with resistance training, it is important to keep the load light enough to allow for higher (read: not slow) speed, multi-joint movements.

There are several ways to manipulate HIIT to achieve a specific metabolic response. Factors such as duration, intensity (load), volume (reps and sets) and recovery time can all alter the outcome of the session. Of these variables, the duration of exercise bouts and recovery periods appear to make the biggest impact.

Benefits of HIIT

HIIT has been shown to increase VO2max (a measure of cardiorespiratory fitness) in individuals with chronic cardiovascular or metabolic diseases when compared to Low Intensity Steady State (LISS) training. HIIT has also been shown to significantly lower insulin resistance in comparison to LISS. The drawback? Due to the higher intensity level of training, it can be difficult for individuals to begin a training program. HIIT also may require additional recovery time between training sessions.

In short, HIIT takes less time, reaps ample rewards and is modifiable. But HIIT is not for the weak at heart.


Low Intensity Steady State (LISS) training is often characterized by reaching “steady state.” What is steady state? So glad you asked. Steady state describes an energy balance between the energy needed by the working muscles ATP (Adenosine triphosphate – energy) production by the body’s aerobic metabolism.

Essentially, in steady state exercise, all energy that is produced is also used, meaning there isn’t any excess to get turned into metabolic byproducts. Think about it this way: you go for a jog on a glorious Saturday morning (70ºF, the sun is shining, allergies are non-existent). You begin to feel your breathing start to even out so you are no longer breathing harder and harder. This is the point you’ve likely achieved steady state. When you change your pace, either by speeding up or slowing down, you may eventually achieve a new steady state once your breathing evens out again for a few minutes.

LISS Benefits

So what helps you lose the most weight? HIIT and LISS actually have no significant difference in terms of fat loss achieved for the same energy expenditure. While HIIT can be more time-efficient as it might not take as long as LISS to achieve the same energy expenditure, LISS is much less strenuous and is largely considered a less daunting prospect for someone who is either new to exercise, deconditioned, or simply “doesn’t have it” that day. Due to a lower level of discomfort during exercise sessions, individuals may be more likely to stick with a LISS program as well. This mental battle is incredibly important when considering an exercise program. After all, twenty minutes of jogging at a steady pace has been shown to improve mood – who doesn’t want that?

Wrap-up – HIIT or LISS?

To summarize, both types of training can be useful, with benefits and drawbacks to both. You can lose the same amount of fat in HIIT as you would in LISS for an equivalent workout (in terms of energy used). HIIT can just reach the total energy expenditure more quickly, making it more efficient. Both HIIT and LISS increase HDL (the good kind) cholesterol levels, so your doctor will likely be pleased (also a win). When starting an exercise program, utilizing LISS is a great way to establish a routine. If you’re determined to perform HIIT, incorporating LISS into a HIIT-based program can also be beneficial to provide active recovery between high intensity sessions. After all, both can exist in the same workout program!

Let’s Train

Looking for more effective ways to train? Check out Athletes In Motion for personal training, small group training, youth training and adult group fitness. AIM’s programs are intentional, modifiable and based around you and your goals. After all, there’s an athlete in all of us!

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