High intensity interval training (HIIT) is a highly effective training strategy to boost your cardiovascular health + fitness, but it’s also one of the most misunderstood concepts across social media.

So, the aim of this article is to explain what HIIT is, what the benefits of it are, and how you can do it.

What is HIIT?

Many influencers across social media will post a video of a circuit of strength exercises and call that HIIT.

That is not what HIIT is.

They are wrong, and have no idea what they are talking about.

So, what is HIIT?

Truth is, there isn’t really any good definition.

Interval training is an easily defined term: a regular alternation between two different intensities of work on the same modality.

Three examples would be:

• Running at 6 mph (10 min/mi) for 2 minutes, running at 8 mph (7.5 min/mi) for 2 minutes, repeat for 4-7 rounds

• walking at 3 mph (20 min/mi) for 0.25 miles, running at 6 mph (10 min/mi) for 0.5 miles, repeat for 4-7 rounds

• Cycling at 60% max HR for 5 minutes, cycling at 90% max heart rate for 1 minute, repeat for 5 rounds

The most common ratios used between the lower intensity of work and higher intensity of work are 1:1 to 5:1.

The point in which this becomes “high intensity” interval training has no working definition, and what the best definition is up for debate. [1]

The intensity you apply to an interval workout is highly customizable, and what the best structure is varies person-to-person.

In general, the aim of HIIT is to spend more time near your maximum heart rate (>90%+ of max HR) than you could with continuous work.

With a well-designed workout, you can spend nearly double the time near your maximum heart rate with HIIT than you could with continuous work. [1]

Health + performance benefits of HIIT:

To build cardiovascular fitness, you need a combination of low intensity work and high intensity work. If you only had time for one or two structured cardio sessions in a week, though, HIIT might be your best bet.

In a sense, it combines the low intensity work and the high intensity work while allowing you to spend more time in the higher intensity zones.

A 2015 systematic review and meta-analysis [2] found that if you HAD to choose between lower intensity, continuous work or HIIT, HIIT is the better choice for improving endurance performance.

It’s worth noting that you’d be better off by having 1 HIIT session in a week along with a higher volume of lower intensity cardio throughout the rest of the week. However, if you’re pressed for time, leveraging in the direction of HIIT is a good move.

Given that endurance (measured by VO2max) is the best predictor of how long you’ll live [3], you can say that this improvement in cardiovascular fitness itself is a health benefit.

However, there’s more than just that.

HIIT has been shown to produce improvements in blood pressure and total cholesterol in healthy populations and in those with existing cardiovascular disease. [4,5] It’s also been show to significantly improve glucose metabolism in individuals with diabetes and healthy populations. [6]

So, whether your motivation for doing cardio is driven by the desire to improve health or performance, HIIT is a beneficial intervention.

How to start doing HIIT:

As previously mentioned, the aim of HIIT is to repeatedly get near your maximum heart rate; thereby spending a substantial amount of total time near it in a single session.

This sort of training is arguably the most stressful on the body. When you’re new to interval training, it’s best practice to start with normal interval training and slowly progress to true HIIT.

So, here’s a general outline on how to do this:

NOTE: to do this most effectively would require a high degree of customization for you. If you want this done for you + help with all other aspects of your training/nutrition; then click here to inquire about 1:1 coaching.

Pick a modality to perform the training on. Some good options include swimming, cycling (road or stationary), running (road or treadmill), AirDyne, Concept2 Rowing, SkiErg, etc.

At first, set your intervals using only subjective intensity. On your ‘hard’ intervals start off with longer, slightly less difficulty intervals.

Using an AirDyne an example of this at first might look like the following:

• 2 minutes of easy pedaling at a ~4-5 / 10 difficulty (~50-65% max HR)

• 3 minutes of moderate/hard pedaling at a ~7/10 difficulty (~75-85% max HR)

• repeat 5x

The first form of progression you would undergo would be decreasing the time of the ‘hard’ interval and increasing the subjective effort of the interval.

You could spend the first week performing the HIIT workout as depicted below. The progressions in the weeks that follow may look like:

• Week 2: 2:00 minutes of hard pedaling at an ~8/10 difficulty

• Week 3: 1:00 minute of hard pedaling at a ~9/10 difficulty

• Week 4: 0:30 seconds of hard pedaling at a 10/10 difficulty

At this point, your next progression could be decreasing the duration of the ‘easy’ interval. It could go as follows:

• Week 5: 1:30 of easy pedaling at a ~4-5/10 difficulty

• Week 6: 1:00 of easy pedaling at a ~4-5/10 difficulty

• Week 7: 0:30 of easy pedaling at a ~4-5/10 difficulty

At this point in this example: you would be pedaling for 30 seconds at a ~5/10 difficulty, pedaling as hard as you can for 30 seconds, and repeating this 5 times.

A final way you could progress this workout is to begin adding rounds. That could look like the following:

• Week 8: 6 rounds

• Week 9: 7 rounds

• Week 10: 8 rounds

• Week 11: 9 rounds

• Week 12: 10 rounds

Finally, you could begin aiming to increase the amount of work done throughout the workout. You should standardize the easy interval to a given speed/heart rate/RPM/etc., but you should begin aiming to complete more work on the hard intervals.

It’s also worth noting that this is by no means the only way to do this. There are endless ways to structure an interval workout and its subsequent progressions. Hopefully, though, this gives you a decent idea of what a good structure looks like.

If you have any unanswered questions about this topic, you are welcome to email me at info@fitnesssimplified.org or comment below. If you want this done for you, I’d encourage you to inquire about coaching here.