High-Intensity Interval Training For Fitness – Your easy guide to the science and practice of interval training.

High-intensity interval training has now achieved the jaunty heights of the exercise fad.  It is the backbone of many exercise classes, personal training sessions and now it even is forming the core of some gyms.  However, like a lot of things in fitness training, it is a simple concept that when applied correctly can have hugely effective at developing your physical fitness or preparation.

High intensity interval training (HIIT) a quick primer.

High-intensity interval training means training at a high percentage of your max heart rate or v02 max for shorter periods of time.  Some research would suggest that intervals of around 2-3 minutes spent at 85% of your max heart rate is the optimum way to elicit a fitness of vo2 max response to training.  The important thing to take away however is your heart rate must rise to 85-100% of maximum for it to be considered “high intensity”.

The intervals provided in a HIIT session need to allow for a full recovery.  Since you will be primarily using the anaerobic and glycolytic based energy pathways this means you will need 3-5 minutes for total recovery.  Methods that do not adhere to this principle are aerobic interval training and not really HIIT since you will not be able to operate at sufficient intensity.

HIIT is a lot more time-efficient than longer duration intervals or more steady-state activity.  One study looking at government advised exercise guidelines (30 minutes of exercise, 5 days per week) put it against 2 HIIT sessions consisting of 2x 10-second sprint intervals (that is not a typo) found they were both as effective for increasing fitness in untrained individuals.

HIIT can be performed anywhere but modalities such as running, cycling, swimming, or rowing carry much less residual fatigue then bodyweight exercises or barbell complexes for example.  Your heart doesn’t care how you train it but your muscles and body does.

A lot of the fitness you will get from HIIT training is from peripheral adaptation (muscle endurance, increase local storage of glycogen, enzymes and increased mitochondria in muscle cells) this makes it feel like it is working very quickly as you will feel the increased muscle endurance in the task almost immediately from session to session.  HIIT is also good at increasing your central adaptations (heart and lungs) but if you want to get really fit there is no escaping needing to increase total volume of training to get a better central response.

HIIT is not a good way of burning fat.  By its very nature, it is very low in calorie burning since the work times are short and EPOC (elevated post oxygen consumption) isn’t some sort of fat loss miracle. Your EPOC from your session will be nothing but noise if you consume 25 jam rolls post-workout.  Calorie control and expenditure is the be-all and end-all of fat loss.

HIIT needs to be goal specific.  For example, If you are doing fitness training for rugby you will get far more out of 2 sessions a week doing HIIT running and hitting bags then you every will from sitting on a spin bike.  This is because the peripheral nature of your adaptation makes training specificity extremely important.

High intensity interval training is very good for athletes who don’t operate in a steady state so if you are an intermittent or sprint based athlete then it is an extremely effective and worthwhile training method.

Implementing HIIT into your fitness programme

HIIT can be done in any manner of ways but to make it truly effective we need an objective measure of what we are doing.  This means having something like a heart rate monitor is incredibly important. It allows us to quantify what we are doing if you don’t have a HR monitor then the use of something like a Watt bike, Concept 2 rower or measured distances and a stopwatch is essential since it will give you power out puts, distances and times. 

What does a HIIT session look like?

Heart rate trace from a HIIT cycling session from a second row player.

Heart rate trace from HIIT running session from a loose head prop.

What you should notice from the above two heart rate traces

  • Intervals are very easy to follow from a heart rate trace as the interval goes on the heart rate rises and as the person takes their rest then their heart rate falls.
  • From set to set or from interval to interval the heart rate response rises and magnifies this is because the effect of fatigue on muscles means each rep becomes more difficult to compete.
  • Running causes, a much steeper increase in heart rate and leads to an overall more intense response.  This is due to the whole body energetics caused by running (actually physically moving your body) and the fact we are physically engineered to run so we are efficient at getting our heart rate up in this manner.

Setting up our work to rest ratio

Session GoalInterval DurationRest DurationExercise ModalityWork to Rest Ratio
Aerobic Improvement2-10 minutes2-4 minutesAny (ideally bike, swim, row or something efficient).2-5 : 1
Aerobic Power15-60 seconds15-60 secondsRunning, Biking, Rowing or an efficient mode1:1
Lactic Tolerance20-60 seconds2-3 minutesAny objective workload.  Specificity is key1:3-5
Lactic Power20-60 seconds2-5 minsAny objective or prolific workload1:3-5

It is important to first identify what you want to achieve from your session. Typically this will come down to either increasing your Vo2 ability or working on your ability to produce power in a set scenario.

The aerobic increases can be done in many non-specific or specific ways and will all add to your ability or fitness.  For the ability to produce power or workload in a specific scenario then training specificity is extremely important.

Doing your lactic training or power output training on a rowing machine is a great general way of doing it but expecting it to make you better at repeated sprint ability will leave you wanting.

If repeated sprinting in a team sport is something you want to train for then you would probably be better served doing repeated sprint intervals or maximal aerobic speed sessions.

Frequency of training

It depends on the total commitment of the athlete and the goal of the training program but generally speaking the following would be a good starting point

Session GoalRating of Intensity (1-10)Frequency per week
Aerobic Improvement3-62-4
Anaerobic Improvement6-81-2
Lactic Improvment / Worst case scenario7-101-2
Speed9-10 (per effort)1-2

Understand this is not an exhaustive list and you wouldn’t run all of these sessions during the same week at the same time. Depending on the time of the season or the balance in your training program this will help to determine the number of times you train any aspect if at all.

Setting out a 4 week HIIT based program.

To finish through this article we will now look at producing a 4-week running fitness program for a rugby player.

We are doing this primarily with the following goals

  • To be done on alternate days from pre-season practice.
  • To improve aerobic fitness
  • To improve repeated sprinting ability

Setting the pace.

To improve something we need to first know how good or poor we are at it as such before we start our fitness programme we are going to test our running fitness as such we will be performing a Mo’Farah or Bronco running test.

Once you have completed the run then you can use it to determine your maximal aerobic pace.  To do this you just take your time to completion in seconds and divide it into the length of the course.

Mo’Farah time = 5 min 30 seconds = 330 seconds.

Total distance completed = 1200m

1200/330 = 3.63 m/s MAS 100%

Now you can use this to set the distances for the following programme

Week 1 – 2 min rest between sets.

Session 1 = 3 sets of 8 of 15 seconds on / 15 seconds off @ 120% MAS

Session 2 = 3 sets of 8 of 15 seconds on / 15 seconds off @ 120% MAS

Week 2 – 2 min rest between sets.

Session 1 = 3 sets of 10 of 15 seconds on / 15 seconds off @ 120% MAS

Session 2 = 3 sets of 10 of 15 seconds on / 15 seconds off @ 120% MAS

Week 3 – 2 min rest between sets

Session 1 = 3 sets of 8 of 15 seconds on / 15 seconds off @ 130% MAS

Session 2 = 3 sets of 8 of 15 seconds on / 15 seconds off @ 130% MAS

Week 4 – 2 min rest between sets.

Session 1 = 3 sets of 10 of 15 seconds on / 15 seconds off @ 130% MAS

Session 2 = 3 sets of 10 of 15 seconds on / 15 seconds off @ 130% MAS

Going back to our original test results we can work out for each session the length required depending on the intensity and the time. For example, in session one we need to complete.

3.63 * 1.2 = 4.35

4.35 * 15 = 65 meters shuttles.

This program will help us to develop our running fitness and our aerobic fitness at the same time and will do so in a time-efficient and specific manner.  However, what if we are fit already (say a 4 min 30 second time in the Bronco test in this instance) and want to work on our own repeatability in high-intensity activities.

Training Work Capacity and Drop off

To work out how good we are at carrying out a high intensity workload and repeating it we need to test our capacity to do so and the drop off between these intervals. 

Identifyng a specific test – we will be looking at high speed sprint ability so we need a test for this purpose below we will be setting out the phosphate decrement test (www.topendsports.com).

Phosphate Recovery Test

  • purpose: this is a test of anaerobic capacity, the ability to recover between sprints and produce the same level of power repeatedly.
  • equipment required: stopwatchmeasuring tapemarker cones, at least 60 meter track.
  • procedure: This test involves seven flat-out sprints, each lasting seven seconds, with 23 seconds recovery. Marker cones are placed two meters apart for the first 20 meters. At forty meters from the first cone, cones would again be placed two meters apart to 60 meters (see diagram). The subjects set themselves at the first cone (Start 1). On the command “go”, each subject would sprints ‘all out’ for seven seconds. At seven seconds, “time” is called and an observer would note at what cone the subject had just past. The subject then has a 23 second passive recovery (walk/jog) period before the next sprint. For the second sprint subjects would set themselves at the last cone (Start 2), facing back along the cones. At 30 seconds after the start of their first sprint, they would sprint again for seven seconds in the direction they had come. Again “time ” is called at 7 seconds, and the distance run recorded. This is repeated for a total of seven sprints.
  • scoring: The drop off distance is calculated by subtracting the distance covered in the last sprint by the distance covered in the first sprint. It is expected that the last sprint would cover less distance than the other sprints due to fatigue.
  • target population: suitable for athletes involved in many multi-sprint sports such as basketball, hockey, rugby, soccer, AFL.

Now we have identified and carried out our test how do we train to get better at it? 

Very simply we run the test as a training exercise or intervals thereof. This will exhibit the best return from training but will cease to be effective after 3-5 weeks without varying volumes or rests. 

What does this mean for training our ability to sprint at high speed repeatable? 

It means we need to train the component parts to produce a better environment for getting better at this test again after another highly specific block of training. In short, we need to target and improve –

  • Our max velocity
  • Our Aerobic power/running fitness.

This means going back to speed training and running more aerobic based interval training.

This exhibits the trap known as training for a fitness test. It is common in a sports setting where performance isn’t measured objectively (as in throwing, sprinting or lifting sports) for conditioning coaches to want to carry out fitness tests to gauge athletes levels of prepardness. This is a solid principal however it can lead to what ever gets measured gets improved. For example a professional soccer team that is focused in hard on a players 5-0-5 agility score will likely train this aspect hard and the conditioner will really push for better 5-0-5 scores.

In another example you might be a crossfitter looking to increase your Grace performance. You could complete the grace workout for time or perform it in intervals to improve at it. And like the above example you will improve for probably 3-5 weeks before you pleateau. To reach higher levels of performance in that standard workout you need to focus on your

  • Clean and jerk, Front Squat and Press/Push press strength.
  • Your aerobic fitness

Once you have improved your fitness in these aspects you will then be able to improve greatly on your previous best after on a few weeks of more specific training.

What it boils down too

If you are training towards a specific goal or end then interval training is an excellent and effient tool you can use to help to improve your fitness. It is something you can do 2x per week and see a really good improvment from if the sessions are laid out in a targeted and approriate manner.

However eventually to develop your fitness to a better level you need to circle back and look at improving your basic or general conditioning levels. This means you need to get

  • Stronger
  • Aerobically fitter

Without increasing your headroom in these two underpinning fitness capacities producing new best levels of fitness becomes challenging if not impossible. When we get into this sort of mindset then we are truly on the path to producing some elite-level fitness.


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