Cardio Wars Part 2 – Why LISS is better than HIIT

What exactly are HIIT and LISS?

Part 1 of our article looked at the differences more in-depth, but a basic overview is:

  • HIIT stands for ‘’high intensity interval training’’, and consists of short intervals of sprinting coupled with low-moderate intensity work.
  • LISS stands for “low intensity steady state” cardio, which consists of purely low-moderate intensity work.

Why do LISS?

LISS is generally performed at a constant pace for between 30-90min, with a target heart rate (intensity) of between 50-65% of maximum. Supporters of low intensity steady state training will often reference the fact that a greater percentage of stored body fat (as opposed to muscle glycogen) is used for energy when performing cardio at lower intensities. As such, many bodybuilders, fitness professionals, and physique-based athletes will perform a LISS cardio workout first thing in the morning during a fasted or semi-fasted state: glycogen stores are used by the body for a number of regenerative processes during sleep, resulting in lower glycogen levels upon waking. This reasons that early morning fasted LISS makes use of these depleted glycogen levels, and taps into fat stores for energy.

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Why LISS is better than HIIT

  1. Active recovery – If you are lifting weights, playing sport, or performing any strenuous exercise, you will be well aware that recovery is the key to making progress between sessions. While high intensity interval training allows for maximum effort in minimum time, it can be extremely taxing when performed more than three times per week, especially when combined with other strength or fitness training. Low intensity steady state cardio helps to increase blood flow to damaged muscle tissue, and is shown to boost recovery.
  2. Less strenuous – A HIIT cardio workout places a huge demand not only on the muscles used, but also the central nervous system, joints, tendons, and ligaments. This has both a physiological and psychological effect on the body, and can deter participants from wanting to continue their cardio routine. LISS is far less taxing on the body in almost every way, especially when performed in a low-impact manner such as cycling or swimming.
  3. Improve aerobic fitness – Due to the extended nature of LISS cardio sessions, aerobic performance is vastly improved. While a HIIT enthusiast might become very good at doing HIIT (anaerobic) workouts; this does not translate very well to real-world activities, or even across different exercises due to the amount of variables in a typical HIIT session (i.e. running vs stationary bike, 30-second vs 10-second high-intensity periods, number of sprints performed, etc). Low intensity steady state cardio, however, allows for participants to utilize their fitness in other areas of their life — 45mins of brisk cycling can improve swimming laps on alternate days, or extend your weekend dog-walking routine dramatically!

While both HIIT and LISS have their benefits, it’s always important to remember to listen to your body. If you haven’t performed cardiovascular exercise in a while, it would be best to start with LISS and gradually introduce HIIT exercises accordingly. Similarly, if you are performing heavy compound movements several times per week AND trying to squeeze in three HIIT sessions, swapping some of these for LISS will allow your body to recover more effectively and efficiently.