High Intensity Interval Training (HIIT) workouts have become increasingly popular over the past year. Individuals now consider HIIT to be a great method of exercise, but few are aware of Low Intensity Steady State (LISS) workouts. Confusion also lies between the decision to perform either HIIT or LISS when trying to maximise fat loss. This will understand the two types more thoroughly and decide the best option for you.

What are HIIT workouts?
HIIT is the name given to any workout that alternates intense bursts of activity followed by a period of less intense activity or rest. This aims to ensure maximum effort in the intense period, reaching 80-95% of individual max heart rate, then allowing it to drop to 40-50% in the less intense and recovery period. This is then repeated on a circuit, for periods of 4 to 20 minutes.
HIIT is found to stimulate metabolism to burn calories at a higher rate even after your workout has finished, this is due to Excess Post Exercise Oxygen consumption (EPOC). This continues after exercise when your metabolism is still raised, therefore, burning more calories than usual in the resting state than normal.

What are LISS workouts?
LISS describes long-duration cardiovascular sessions which aims to maintain your heart rate at 45-60% of individual max heart rate for the duration of the workout. Aside from the warm up and cool down phases, there is little or no change in the speed or intensity of the workout.

Benefits of HIIT and LISS
Both forms of training have demonstrated improved fitness. Improvements to aerobic and anaerobic fitness levels, consequently improve blood pressure and cardiovascular health. Alongside improved heart health, these workouts have also been demonstrated to improve insulin sensitivity and cholesterol profiles. They also target abdominal fat and body weight while maintaining muscle mass.

Both LISS and HIIT are effective cardiovascular training methods, however, how effective depends on the individual. LISS has been shown to support fat loss. Fat is the primary source of energy, therefore essentially exercise is burning fat. Therefore, long but moderate intensity workouts allow fat burning over a longer period. However, when we perform high intensity workouts, carbohydrates are used as the primary source of energy and fat as the secondary. This is important dependent on an individual’s goals, e.g. weight training or marathon running.

Many studies have been conducted comparing HIIT and LISS for fat loss. HIIT workouts have shown more favourable results when directly compared to LISS for both fat loss and cardiovascular fitness.

A study in 2014 demonstrated that HIIT is superior to LISS and therefore a better choice for individuals trying to improve your fitness. HIIT was also found to be more favourable, when studying a 12-week program resulting in significant reductions in total abdominal, trunk and visceral fat in overweight males. An older study also found that those participating in HIIT maintained lower body fat and lower waist-to-hip ratios than those participating in LISS.

As previously mentioned, HIIT boosts EPOC thus burning more calories resulting in more fat burnt. There is a direct link between exercise intensity and EPOC duration, the higher intensity the longer the effect. LISS was found to give negligible EPOC effects meaning there is little change to your metabolic rate. When you perform LISS, you only get that calorie burn at the time you perform your cardio, therefore showing that HIIT can be more beneficial for you.

The take home message is; both methods do work for fat loss. Choosing which one will work best for you depends on factors such as, your current fitness levels, the time you have available and injuries or medical conditions that may limit your performance. For HIIT to be the most beneficial, it is important that you maximise input and if you’re unable to, LISS may work better. However, based on previous evidence, if you are able then it may benefit you to choose HIIT cardio where possible to see results quicker, if this is your preference. Combining your HIIT sessions with resistance training to see even bigger changes in your body shape and lean muscle.