Hiit vs liss cardio - the facts

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1 Hiit vs liss cardio - the facts With high intensity interval training (hiit) gaining so much media attention many people have started to utilize this cardiovascular format into their workouts. For many this will elicit more fat being utilized as energy post workout- creating the 'after burn'. Low intensity steady state (liss) is what most gym goers do overtime they walk in the gym. This is the form of cardio that as the name suggests- steady state, meaning you're generally working at a set intensity for a certain period of time generally on a typical cardio station such as the treadmill, bike or rower. For years cardio has been classed as the most effective exercise form for 'fat burning'- however over the years and with advances in research this has been flawed. Resistance training has been shown to be more efficient for composition due to its effects on the endocrine (hormonal) system and metabolism. With that said I am not suggesting all cardio should be dropped in favour of resistance training. Cardio is a fantastic tool for improving heart function- the most important muscle in the body, along with many other benefits. In this article I will discuss both hiit and liss cardio and by the end I hope you know what is best for you. Hiit High intensity interval training as the name suggests are based around intervals, these intervals alternate between high intensity intervals such as an all out sprint for 30 seconds, followed by a lower intensity interval such as a brisk walk for 6 seconds. The intervals repeat and the ratio of sprint to brisk walk could be anything from 4:1 to 1:2, individual fitness and experience dependent. Hiit burns more causing greater energy demand post workout through a process called EPOC- excessive post- exercise oxygen consumption. The oxygen is what makes the magic happen, and the huge demand for it during hiit creates the elevation in metabolism post workout. Oxygen is used to break down carbohydrates and fat as energy. When muscles contract they require energy, and the greater the contraction and repetitive speed of which the contraction(s) occur causes

2 us to hit our lactate threshold. This is where the body is producing more lactic acid than it is burning. We can only get so much oxygen to working muscles and working at such a high intensity causes an oxygen debt. Post exercise the body still requires oxygen at a higher rate. Simply put, the higher the heart rate the more oxygen is required and the further the body is taken out of homeostasis (balance) thus more energy being used post workout to restore balance and bring it back to its original state. Another benefit of hiit is the increase in catecholamine s (epinephrine and norepinephrine), which help free up fatty acids to be used as energy. Once these stored fatty acids have been freed they can enter the mitochondria to be used as energy. Mitochondria are the bodies power plants of energy. Their primary task is to use the nutrients we eat and store into energy. This energy is used for a whole host of tasks from breathing to exercising. Without getting into cellular biology the mitochondria are essential for energy production and with regards to fat loss, fatty acids must be freed from fat tissue and sent to the mitochondria to be used for energy production- where the so called 'burning' occurs. The more mitochondria an individual has the greater oxidative capacity there is for fat loss. HIIT increases mitochondrial capacity and you actually increase the amount of mitochondria you produce. Studies show that you get greater fat loss through high intensity training because of the increase in oxidative capacity. Whereas with lower intensity cardio you re only burning calories in that moment, there is no prolonged elevation in metabolism. For fat loss you need elevated metabolism to increase the rate in which your body burns calories. With hiit you are burning calories at the moment, which are coming from carbohydrates and fatty acids that are being freed up. You are actually changing the muscles metabolism and its ability to burn fat by increasing the mitochondria density of your muscle, so you increase the muscles oxidative capacity - allowing you to burn more calories. Those who have/are trained with me will be familiar with me talking about the endocrine system and how hormonal function is the major contributor to success and failure with regards to body composition. Certain hormones break down tissue (catabolic) and increase fat loss while others can trigger

3 fat storage (lipogenic). Exercise causes certain hormones to be secreted and lowers the secretion of others. The benefit of hiit training with regards to the endocrine system is that when your heart rate rises and you approach 85 to 95% of VO2max, growth hormone, testosterone, endorphins, epinephrine (adrenaline), norepinephrine (noradrenaline), cortisol, and aldosterone all increase. These hormones all have effects on body composition and anabolism. Positive hormonal response from liss cardio is minimal. One other note on cardio is the obsession we have with counting calories on machine gauges. People try to burn as many calories as possible but the calculators can't tell you where the calories are coming from, and this is can cause problems with regards to muscle tissue. When the body comes under stress- which cardio places on the body, the body can start to break down muscle tissue through elevation in the stress hormones cortisol. Cortisol is an essential hormone which is vital for many functions within the body, however when it gets released in excess it can start breaking down muscle tissue to be used as fuel, rather than stored carbohydrate or fat. Look at a marathon runners body compared to a sprinters A sprinters body will have lower levels of body fat and more muscle tissue. This is due to better control of cortisol release. Simply put there is such a thing as too much exercise when it comes to long bouts of cardio, and muscle tissue can be sacrificed. Remember muscle tissue burns fat and keeps it off long term so start losing it and effectively you're lowering your metabolic rate. Hiit benefits: 1. Increase fat loss while retaining lean muscle tissue 2. Increase lung capacity (vo2 max) 3. strengthening the cardiovascular system 4. Increases work capacity - allowing you to exercise for longer at a high intensity

4 5. Improves the oxidization of fats and carbs in muscle tissue 6. More challenging to the fast twitch muscle fibres the fibres that are needed for strength and power 7. Increases fat burning hormones 8. Can reduce resting heart rate 9. Reduce blood pressure From the above you can see there are many benefits to putting hiit into your workouts, but considerations should always be taken when approaching this method. Firstly consider you or your client s weight- are they carrying a lot of excess weight? Running for example puts 3 times your bodyweight through your knees joints. Most people who are overweight don't have the appropriate foundation from a biomechanical perspective to start generating such force through their joints, this would just result in injury. Secondly what is their/ your current fitness level- you don't run before you can walk. So an individual fairly new to exercise wouldn't be wise to start with a hiit programme. From a dietary perspective those on a low carb/ ketogenic diet may not be wise to follow such an intense format due to the stress being put on the body while it's in a glycogen (carbohydrate) depleted state. Hiit workouts can be done on any cardio station or can be done using bodyweight movements such as burpees, squats and push- ups performed in circuits. For those who play sport try and incorporate movements that complement that sport. For a footballer do sprints, basketball or volleyball player do a movements that involves jumps and for boxing do heavy bag work. Regardless of the exercise just remember that in your high intensity burst you're trying to elevate the heart rate. As you progress a variable that should change is the ratio of the interval times. So where you may start working to a 3:1 ratio which for example

5 would be 90 steady paced rowing followed by a 30 seconds sprint, the next step would be to change the ratio to 2:1, 60 seconds to 30 seconds. As the weeks go on and the more efficient the body becomes the ratio could even change to 1:2 meaning the sprint would be longer than the rest period. Naturally this would only be relevant for an experienced or highly trained individual, who would most likely shorten the total workout with the greater increase in the sprint volume to rest. Liss Reading the above you'd think there is only one winner in the hiit vs steady state debate. Like most forms of training every format will be best suited to certain individuals whilst others will benefit from a different stimulus. When it comes to liss there are many benefits. Many people do not have the endurance, speed, experience and joint mobility to start using hitt. For those who fit that criteria, lower intensity cardio would be favorable. Stress is a major factor in contributing to fat accumulation, and that applies to everyone. An obese individual for example would not tolerate the stress hitt training would place on their body and would benefit more from a brisk walk as a starting point, as compositions and cardiovascular health starts to improve and body fat starts to decrease that is when intensity can step up a notch. Personally I feel the type of cardio also needs to be chosen in conjunction with both goals and diet. For example building muscle generally requires a moderate to high carbohydrate intake and so hiit would be favourable, as it will keep metabolism raised and won't run the risk of breaking down muscle tissue, which long bouts of cardio can do. Losing fat on the other hand generally requires energy deficit and with that carbohydrates are generally lower. This means that stored carbohydrate (glycogen) is general low as is energy. Hitt training along with resistance training could be too demanding on the central nervous system making liss favourable in this situation. Liss can be incredibly boring and yes people may argue there are more effective ways of

6 burning fat. One thing I have found in the past is the benefit liss training has on recovery. Resistance training causes muscle to tear and swell which can cause doms (delayed onset muscle soreness) so for those of you familiar with legs days know all about doms. In the past I've woken up after leg day struggling to walk down the stairs, but by cycling or walking on an incline the day after I found the soreness drastically reduces. This is to do with increased blood flow. Blood transports nutrients such as amino acids, which aid recovery. When it comes to fat being utilized during cardio liss actually gets 65% of calories burnt from fat whereas hiit gets 50%. Obviously having read the above you're familiar with hiit causing more of an elevation in metabolism long term however during cardio liss burns more fat. When the heart rate reaches bpm studies have shown this is when the body is primarily burning fat as fuel, so when you hear about 'the fat burning zone' that is what it is in reference to. Intensity will always be the important factor when it comes to cardio rather than duration. That said, certain factors that have been mentioned above need to be considered. This article hasn't been written to favour of a particular method, but rather to educate you on the benefits of both hiit and liss. Hopefully having read the above you know what is best for you.