GIrl sprinting

When it comes to getting fit what would you do?

For the most part, people think they should go for a long run, that is 5km or more running at a steady and comfortable pace. Conversely, someone else might believe lifting weights, doing Pilates or trying to get in as many sprints within an allocated time is the best method to get fit.

Believe it or not, none of these answers are incorrect.

However, for an individual to be ultra-fit, a certain amount of cardiovascular training needs to be completed, but the key question here is; “What type of cardio?”

The problem today is that the word cardiovascular fitness has so many different names all meaning the same thing which makes it a little confusing. For example; metabolic conditioning, HIIT, aerobic and anaerobic capacity.

The first step is to determine what type of fitness you need to develop. This term within sport science is known as Specificity– the principle of training that states that sports training should be relevant and appropriate to the sport for which the individual is training in order to produce a training effect. For example:

  • Marathon Runner would primarily do long distances at a constant pace
  • 100m Sprinter would do high intensity efforts with long rest breaks
  • A footballer would have a mix for long distance running and sprints
  • An individual looking to shed fat would primarily do high intensity efforts with some supplemental endurance training

The second step is to understand the basic principles of energy systems within the body and how they interplay. In doing so, it will help you determine what energy system you should primarily target thus what type of cardio you should perform in order to reach your fitness goals. There are three energy systems which help the body produce energy

ATP-PC System (Explosive energy system)








This energy system provides rapid, high bursts of energy which initiates at the very beginning of the activity. However it only produces optimal energy for 3-10 seconds hence it does not require oxygen for fuel. Athletes who require explosive movements such as sprinters or weight lifters primarily focus their training in this energy system

  • Anaerobic System (high intensity activities)


This system provides medium to high intensity burst of energy for activities that last from 10sec to 2 minutes. As a result, this system produces an accumulation of lactic acid within the blood and muscles causing a burning sensation in the muscle and fatigue. The primary difference between this energy system and the ATP-PC system is capacity. That is, the amount of time it can work at peak output before dropping off.

  • Aerobic System (longer duration activities)


The aerobic system is the most utilized in any sport or task and provides energy for long periods of time. It relies on oxygen for fuel thus, can help remove the lactic acid build up in the muscles. Activities that are continuous in nature such as running or swimming heavily rely on this system.

It is important to note that there is an interplay of all three energy systems throughout the whole session however the capacity of each system drops in and out depending on the exercise and duration.

Conversely, the aerobic system doesn’t need a rest break when training. So if you are currently doing HIIT training but not having any rest breaks you are actually not training the “explosive systems” but rather the aerobic system causing you to develop different adaptations than what you want

Let’s take a closer look at these energy systems.

As already mentioned, the two most common training types are aerobic training and high intensity training or repeat anaerobic effort.

Aerobic training is primarily done in low to moderate intensities and remains constant. For example going for a 5km jog, bike ride, or walking on a treadmill (or anything along those lines).


Heart rate ideally should be between 120-160bpm. The duration varies, however most commonly sits around 20-60minutes. This form of training has long been a key component in training programs. AFL teams pre-season tend to be heavily focused on this specifically because any activities that are anaerobic (explosive movements) in nature such as sprinting heavily depend on the aerobic system which assists in recovery rates after each bout or effort. The greater your aerobic capacity, the quicker you can recover, the more high intensity efforts you can get into a workout. Therefore the greater you aerobic capacity, they better you will be at everything else. For example, HIIT training, weights training or even just walking up those killer stairs at work. You won’t be out of breath for as long!

This form of training improves stress levels and recovery, whilst delivering general health benefits showing us that steady-state cardio is an oldie but a goodie. However, you will only burn fat during the training session and if your pace is relatively slow chances are the amount of calories burnt won’t be substantial.

HIIT (High intensity interval training) commonly include things like sprinting, Kettlebell swings, power ropes, prowler or sled sprints, timed laps in the pool or basically any activity that allows you to work at a high intensity. Athletes commonly use this method nearing the end of pre-season to shift their VO2max levels to the right (fitness levels improve rapidly) and to improve explosiveness.



HIIT and Fat Loss

It is now common practice within a lot of gyms to utilize high intensity intervals in order to help clients shed some fat (you will notice here at the Fit stop we do this). In plain physiological terms, HIIT training puts your body above lactate threshold allowing you to produce greater improvements in metabolism thus leading to increased fat loss. In essence, metabolism is boosted by the increase number of energy producing units called “mitochondria”. This system produces ATP (note this is the fuel used by the first energy system ATP-PC) and is also the location for where fat is utilized. So, through HIIT training mitochondria density will develop within the muscles, increasing mechanisms which burn fat.

Even more exciting, you will continue to burn fats for up to 3 hours post training (unlike aerobic training). This is why a lot of people looking to drop fat do HIIT.

Hit graph

Figure 2: Comparison of metabolic rates (calorie burning) between HIIT training and aerobic training

So where does this leave us?

Both methods provide great health benefits and both seem to burn fat. From a sport science background myself I am a strong believer that the best cardiovascular fitness improvements occur from a mix of high and lower intensity training that must be tailored specifically to an individual.

Both aerobic and HIIT training are effective in their own ways and should be included in any training program. Just because HIIT training is beneficial in weight loss doesn’t mean it’s the only form of cardio you should do. One of the biggest misconceptions in the fitness industry is that both aerobic and anaerobic capacities are improved with HIIT alone which couldn’t be further from the truth. Aerobic and anaerobic training place different stressors. So if you find:

  • It extremely hard to do 10 minutes of HIIT training
  • Find it hard to recover between efforts e.g., sprints or kettlebell swings
  • Cannot run any longer than 10minutes without feeling puffed
  • Recovery rates between training sessions are average

You should look to add in some aerobic training to improve your aerobic capacity


Take Home Points:

Aerobic training (low-moderate intensity)

Pros Cons
  • Can lower body fat percentage
  • Increases aerobic capacity
  • Improves stress and wellbeing
  • Improves recovery rates between high intensity efforts
  • Helps lower cholesterol
  • Normalizes blood pressure levels


  • Increases the chance of overuse injuries eg. Hip, knee, lower back
  • Might put your body into a catabolic state (eating up muscle instead of carbs as fuel) if you run every day for a long duration and don’t eat correctly
  • Loss of too much muscle will slow the metabolism
  • Can become boring
  • Not great on knees


HIIT or Anaerobic training (high intensity)

Pros Cons
  • Fat Loss with no muscle loss
  • Burn more calories in a short period of time
  • Build lean muscle which boosts metabolism
  • Burn calories after training for up to 3 hours
  • Reduce chance of boredom as there are a variety of exercises
  • Short duration training time
  • Great health benefits
  • Extremely strenuous
  • Need to put your body into an extremely uncomfortable state to reap rewards
  • Need a baseline strength
  • Increase chance of injury
  • Can lead to dizziness or vomiting
  • Doing too much too soon can cause extreme muscle soreness
  • Training too hard to often can actually cause your fitness to plateau


By Katrina Laczoffy

If you got anything of value from this post, feel free to click the ‘Like’ button below 🙂