By Myprotein Writer Paul Jowsey
Cardio and the benefits for fat loss are well known and apparent, however, confusion often lies between the decision to perform either LISS (low intensity steady state exercise) or HIIT (High Intensity Interval Training) cardio when trying to maximise your fat loss.
What are HIIT Workouts?
High-Intensity Interval Training (HIIT) describes any workout that alternates between intense bursts of activity followed by a period of less-intense activity or even complete rest period.
The aim is to train at the highest intensity possible for short bursts, reaching 80% to 95% of an individuala maximal heart rate, then allow the heart rate to drop back down to around 40% to 50% during the recovery phase.
This is before going again and completing as many intervals of high intensity bursts as possible during each session.
What are LISS Workouts?
Low-intensity steady state cardio (LISS) is how it is described. These long-duration cardiovascular sessions work at a target heart rate of 45-60% of your estimated maximal heart rate.
There is very little or no change in the speed or intensity through-out the work excluding the warm up and cool down phases.
HIIT & LISS: The Health Benefits
Both forms of training have been shown to improve:
– Aerobic and anaerobic fitness levels
– Blood pressure
– Cardiovascular health
– Insulin sensitivity (helps muscles useglucose for workout fuel)
– Cholesterol profiles
– Abdominal fat and body weight while maintaining muscle mass (ACSM, 2014)
HIIT Vs LISS
Both HIIT and LISS are effective forms of cardiovascular training for different individuals.
LISS has been shown to support fat loss due to the fact that when we exercise at low and moderate intensity, fat is the primary source of energy – we are ‘fat burning’.
When we exercise at high intensity, carbohydrate is used as the primary source of energy, alongside fat as the secondary source. This may be important information for some depending on their type of goal e.g. weight training/marathon running.
Many studies recognise that both forms work for fat loss, however, it seems that HIIT Workouts have shown more favourable results when directly compared to LISS – for both fat loss purposes and for cardiovascular fitness.
In terms of your fitness improvements, HIIT is superior to moderate-intensity continuous training in improving Cardio Respiratory Fitness (Alahmadi MA, 2014), showing that it can be a better choice over LISS to improve your fitness levels.
When we again look at HIIT from a fat loss perspective, the results more favourable. For example, a 12-week program resulted in significant reductions in total abdominal, trunk, and visceral fat in overweight males (Alahmadi MA, 2014).
Another study compared average-weight females performing either LISS or HIIT – only those performing HIIT were found with a decrease in body fat percentage and those using LISS had no such changes in their body fat (Bryner et al, 1997).
Another direct comparison to LISS was undertaken with 2500 men and women. It was found that those participating in HIIT maintained lower body fat and a lower waist-to-hip ratio’s than their 38 counterparts participating in LISS (Tremblay et al, 1990).
HIIT continues post work out
HIIT is thought to stimulate your metabolism to burn calories at a higher rate even after your workout has finished.
This is due to post-exercise period is called ‘EPOC’ – Excess Post Exercise Oxygen consumption. This is the period after an exercise when your metabolism is still raised, allowing your body to continue to burn calories whilst in a resting state, even more so than usual.
The body weight reduction we get from HIIT may be due to the post exercise metabolism boot, EPOC, which appears to be mainly supplied by fat during recovery (Tjonna et al, 2009), burning fat at rest post HIIT!
There is a direct link between exercise intensity and epoc duration. The higher intensity you work at the longer you get the epoc effect (Bhar & Sejerstead, 1992). Liss was found to give negligible epoc effects meaning there is little or no change to your metabolic rate from steady state cardio.
With HIIT and EPOC, this means you will burn calories at a higher rate even after your session has finished. It creates metabolic changes to ensure that you are burning calories at a higher rate for hours after your work out!
When you perform LISS, you only get that calorie burn at the time you perform your cardio, again showing that HIIT could be more beneficial for you.
Take Home Message
Both forms of cardio work for fat loss – which one you choose depends on other factors such as your current fitness levels, the time you have available to work out and if you have any injuries or specific medical conditions.
In terms of just getting results, based on evidence from studies and with my own client base, it may be benefit you to choose HIIT cardio where possible.
HIIT is more challenging and you will naturally fatigue quicker then LISS – the more intervals you perform the longer the heart rate will take to come down – if your new to HIIT, expect this to happen and gradually build up to performing several intervals per session. Also, as obvious as it may seem, remember to always warm up and cool down to gradually raise and help decrease your heart rate.
Combine your HIIT sessions with resistance training to see real changes in your body shape and lean muscle!