So you all must have come across these terms if you go to gym, if you are a fitness freak, a sports person or while simply scrolling through fitness pages on social media or internet.
Well, both have their own benefits. What you should do or choose between these two purely depends on your goals, level of fitness, years of practice or how long you have been hitting the gym and ofcourse how well versed you are with form and techniques of exercises.
So first of all I would like to discuss about energy systems in our body, how they work and how they are used while doing an activity and the outcome or effects on our body. So it will later easy to understand about the difference between HIIT and LISS.

Our body has phosphogen system, glycolytic system (consisting of fast and slow glycolysis) and oxidative system. When a short duration activity is performed at high intensity, for e.g. activity which lasts for 0-6seconds. After that it is phosphogen and fast glycolysis that comes into action which lasts from 6-30seconds.
Fast glycolysis works for 30 seconds to 2 minutes later on it moves to 2-3minutes for fast glycolysis and oxidative system and any activity going for more than 3 minutes will go into slow glycolysis and oxidative system.
During an activity which will be lasting for 0-6s, the body uses ready ATP-CP (fuel for body to work) for energy. Called as phosphogen system. As the duration of activity increases and ready ATP-CP gets over, body breakdowns the glucose initially to generate ATP for ongoing activity (phosphogen and fast glycolysis) As the duration keeps increasing body breaks glucose and fats for energy (fast glycolysis) i.e. it breaks glucose and fats to generate ATP to complete given task.
Once the glycogen stores starts to deplete and the activity becomes slower body breaks more of fat to generate ATP (slow glycolysis) for energy and later on just fat for energy which is called as oxidative system. Now let’s talk about HIIT and LISS.

HIIT stands for high intensity interval training. So as the name suggests, it ishigh intensity activity, surely beginners or people who just started moving their body cannot directly go for this.
High intensity interval training is a form of training that uses repeated high intensity exercises bouts with a small recovery time in between. It usually stresses the anaerobic or fast glycolysis system.
To get maximum benefits of HIIT, person has to do it at 90% of VO2 max or above. As the activity is very intense the work to rest ratios are higher.
For e.g. W: R 1:16, 1:20. Taking too long breaks can diminish the benefits and too short breaks can lead to injury or early fatigue.
HIIT also helps to improve the lactate threshold capacity and energy economy. As with the fatloss point of view it won’t really be beneficial to great extent because it usually stresses the fast glycolysis where body uses mainly glucose and less amount of fat for energy. It is best for athletes, and general population too but if they have good training experience.

LISS is low intensity steady state cardio or activity which can be performed for 45-60mins at 50-60% of VO2max and it emphasizes on slow glycolysis or oxidative system. Slow glycolysis system uses majorly fats and less glucose for energy. When in later stage you enter the oxidative system the body will use fats for energy(from adipose tissue or fat cells) for energy resulting in fat loss.
It is best suggested to do LISS on empty stomach to get the most of it because in the absence of glucose body will break more fats for energy required to perform the activity.
About The Author
Anthony Cardoz is a certified Personal Trainer from K11 Academy of Fitness Sciences. He has experience of 3 years in the fitness industry. He is a fitness freelancer writer at b..
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