Posted on Friday, 4 May 2018


The age old question; which type of cardio is best for fat loss and preserving muscle tissue? As it would seem, every so often, new research comes to light to support differing sides, which leaves us just as confused as we were to begin with. The first school of thought is to strictly implement High Intensity Interval Training (HIIT), whilst the other side of the fence is strictly for Low Intensity Steady State (LISS) cardio. Which is best? Let’s discuss.

It goes without saying, cardio is a proven tool which assists with fat loss, alongside sound dietary protocols and weight resistance training. However, any form of cardio can be perceived as a two edged sword, which could potentially hinder the desired end result; the preservation of lean body mass/muscle tissue, once fat loss has been achieved. Furthermore, it can prove detrimental toward training performance, strength preservation, an individual’s hormonal profile, energy levels, libido and mood. As we’ll see, both methods of cardio have their pro’s and their con’s, we’ll also give you an insight into how to choose the most appropriate method for your goals.


Cardio in its essence, is associated with continuous and monostructural methods of exercise such as running, walking, cycling, swimming etc. this is more commonly referred to as LISS and has long been a traditional and favoured choice of bodybuilders, physique competitors and fitness enthusiasts alike. There are several benefits toward increasing cardiovascular health as well as remaining a tried and tested method to assist the loss of fat tissue.

With that being said, in more recent times the rise of the popularity of HIIT as a primary method of cardio, simply cannot be ignored. Granted, there have been numerous studies conducted, which of whom suggest an improvement in performance, continual and more efficient fat loss as well as better muscle preservation.

During both forms of aerobic exercise there is a number of short term (acute) and long-term (chronic) cardiovascular responses and adaptations that occur in the circulatory, respiratory and muscular systems.

Such short-term (acute) responses are known to:

  • Increase Heart Rate
  • Increase the Rate of Respiration (Breathing)
  • Increase Cardiac Output
  • Increase Fat Oxidation
  • Increase Acute Energy Expenditure

Such long-term (chronic) responses are known to:

  • Decrease Resting Heart Rate
  • Increase Cardiac Hypertrophy
  • Increase Blood Volume
  • Decrease Recovery Times
  • Increase Resting Metabolic Rate
  • Increase Chronic Energy Expenditure
  • Increase Strength of Respiratory Muscles

Both methods of cardio have truly been tried and tested, providing the desired end result, yet for all purposes, we ask the question; which is better? As we’ve established, both have merit for a variety of reasons, but the answer is quite simply – it depends. For the most part, the following advice will assist you to make a more informed decision as to which method to choose.


Low Intensity Steady State Cardio is generally performed for longer bouts than its “rival” HIIT, typical sessions commonly last anywhere between 30-60 minutes, with the individual’s heart rate between 50-60% of maximal capacity. The concept is rather simple, that a greater percentage of stored body fat as opposed to muscle glycogen (stored glucose) is used for energy when performing cardio at lower intensities.

Due to this fact, it is by no means uncommon to see individuals performing their LISS in a fasted or semi-fasted state. The theory is as so; Overnight glycogen stores are used by the body for a number of regenerative processes during sleep resulting in lower glycogen levels first thing in the morning upon waking, therefore the reasoning behind early morning fasted LISS is to make use of these depleted glycogen levels and tap into fat stores for energy.

However, this theory has come under recent scrutiny, an extensive topic which we will explore at a later date.

In summary;


  • Shown to directly use a greater percentage of calories from fat rather than glycogen
  • Provides active recovery to help recovery from resistance training
  • Less taxing on the CNS and muscular system
  • Easier on joints, ligaments and tendons
  • Is not psychologically taxing
  • Much easier to prescribe for sedentary and overweight populations


  • Sessions are often frequent, long and tiresome
  • Few calories are expended after the exercise session
  • The body adapts quickly to LISS reducing its metabolic benefits and total calories expended


Conversely, HIIT is a method of cardiovascular exercise that utilizes a combination of smaller, more intense bouts, ranging from 10-60 seconds in duration, which is then alternated with appropriated rest periods/low intensity activity.

In modern times, we have seen an exponential growth in the popularity of HIIT among athletes and individuals alike, largely due to the shift in training for performance and aesthetic appeal. A lot of the anecdotal reasoning behind HIIT training for physique based athletes is that it more similarly resembles the demands of resistance training and as such may help promote similar adaptive processes such as greater muscle retention.

The premise behind HIIT is an increase in metabolic rate (and hence calorie burn) long after the session has ceased. These benefits are due to a phenomenon otherwise known as Excess Post-Exercise Oxygen (EPOC). EPOC can be summarized as the amount of oxygen required to restore the body to its natural state; a physiological effect that explains the after-burn of calories.

In addition, HIIT places a greater demand on the anaerobic (oxygen lacking) pathway to produce ATP, the energy currency of the body. Because of this, during the post-exercise recovery period the body will take in more oxygen for regenerative processes including the re-synthesis of muscle glycogen, production of ATP, and to help the body repair muscle tissue damage.


  • Quick workouts that do not require much time to complete
  • Burns a lot of calories in short periods of time during exercise
  • High amount of calories burnt after exercise
  • Greater impact on metabolic pathways
  • Can encourage the preservation of lean muscle mass
  • Promotes both aerobic and anaerobic work capacity


  • Workouts are often physically and psychologically demanding
  • Taxing on the CNS and muscular system
  • Greater risk of injury
  • Greater impact on recovery and must be programmed accordingly
  • Not suitable for all populations


Before we give you the answer that you’ve been waiting ever so patiently for, it absolutely and undeniably, goes without saying that for optimal fat loss and muscle retention; creating a total daily caloric deficit through a sound nutritional strategy is a prerequisite. One’s emphasis should always be directed toward regular weight resistance training and a controlled caloric intake, before looking to any form of cardio.

Now that we’ve established that both LISS and HIIT have their respective places for fat loss and muscle retention, it is in fact clear that HIIT inevitably leads to more efficient fat loss, in a shorter time frame, whilst improving muscular metabolism, oxidative capacity whilst having a significant effect on enhancing an individual’s metabolic rate (leading to further fat loss).

However, too much of a good thing inevitably becomes a bad thing. HIIT will succumb to the law of diminishing returns, once it becomes increasingly difficult to recover, taxing on the individual’s joints and negatively impacting their weight training performance.  Therefore, it would be wise to use LISS strategically, to counteract the aforementioned “downsides”.

Despite that LISS can be time consuming, monotonous and has a significantly slower rate of caloric burn, it can prove to be less obtrusive whilst simultaneously assisting recovery between weight resistance sessions.

It is for these reasons, that a combination of both methods can be considered the “best” approach when looking to maintain workout intensity, preserve lean mass and maximize fat loss. The duration and frequency of each will very much depend on the individual and their desired weight loss target, desired time frame, metabolic capacity and nutritional adherence.