HIIT vs LISS Training…it is an emotive topic! Which is the most effective way for fat loss – High intensity interval training, or low intensity steady state cardio? They both offer a great way to develop your cardiovascular system but have quite different effects on the body. There are positive and negatives to both types of training, so let’s have a look at both.

High Intensity Interval Training (HIIT) workouts are performed at maximum capacity for a specified period of time (between twenty seconds and one minute). Then you rest for a short period of time (between 10 seconds and 1-2 minutes) before repeating the exercises. The cycle is repeated until you can barely stand – or breathe!! (five times or more). High intensity training creates metabolic changes and can improve body composition, helping to retain lean muscle mass whilst losing body fat – how does it do this?

Mitochondria are your body’s energy powerhouses.The more mitochondria you have and the more active they are the greater oxidative capacity you have for fat loss. HIIT increases mitochondrial capacity and you actually increase the amount of mitochondria you produce.

Examples of HIIT training include Tabata intervals, (20 seconds on and 10 seconds off) or exercises such as burpees, box jumps, mountain climbers, jumping jacks, performed at a ratio to suit your fitness level. This type of exercise is performed for between 5 and 15 minutes. Any more is just not necessary – and not usually possible, if you are going at maximal power. Performing HIIT style workouts improves your metabolism, and when that happens you can expect more fat loss over time.

Low Intensity Steady State cardio (LISS) in contrast, only burns calories during the time you are exercising but it plays an important role in developing your different energy systems, helping with cardiac health, and even promoting recovery from sore muscles. Low Intensity Steady State cardio is any aerobic exercise that you perform at 60%-70% of your maximal capacity for 20 minutes or more. The pace should remain the same during the whole exercise (wearing a heart rate monitor can help you to keep your heart rate within the appropriate range). Examples include Walking, Jogging, Cycling, Elliptical, Swimming.

Doing too much cardio exercise however, can have a negative effect because your metabolism adjusts to the pace, resulting in the need to increase the number of sessions to continue seeing results. These types of workouts can also become boring and repetitive if performed too often. Individuals who participate in endurance exercise to the exclusion of other types of training (commonly known as “chronic cardio”) may experience conditions such as atrial fibrillation (abnormally fast heart rhythms) which can lead to scar tissue formation in the heart, excessive inflammation in the body and increased risk of myocardial injury. Chronic cardio can also lead to repetitive strain and joint injuries.

High Intensity Interval Training on the other hand is not for everyone as the point is to push yourself to maximum capacity, which can feel uncomfortable, may make you nauseous when you first start incorporating this type of exercise into your routine, and has a higher risk for injury. And, in contrast to LISS, HIIT workouts should not be performed 5 or 6 days a week because it will have a negative impact on any resistance training you may be doing, and places too much stress on the central nervous system. Twice a week HIIT sessions, or sprints every 7 to 10 days, is plenty to reap the benefits of this kind of training.

Combining both HIIT and LISS workouts into your weekly routine is an ideal way to get the best out of your training, (along with some resistance training – but I’ll save that for another day!)

Finding the right balance for you means that you can be both the tortoise AND the hare!

What exercise do YOU include in your weekly routine?