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Most of us can't spend hours at a gym in the morning or evening, or spend every afternoon in the pool or on the trail. However, most of us also recognize that we need to train our cardiovascular system regularly. Simply put: exercise takes time, but we don't have much of it to spare. Is there a solution that allows us to maximize the little time we already have available? Yes, and it's called high intensity interval training--HIIT for short.

HIIT has grown in popularity over the recent decades. It's been used by many people in many different professional, amateur and recreational populations to enhance anaerobic and aerobic capacity. But what exactly is it?

The simple answer is that it is a short period of high intensity activity, followed by a period of active recovery or rest, repeated for a specific number of cycles. The most famous--and perhaps the hardest--HIIT protocol is the Tabata, named after a paper by a Japanese scientist of the same name that was released in the 90s. The classic Tabata variant is 20 seconds of maximal work, followed by 10 seconds of rest, repeated 8 times. Alongside the Tabata protocol, there is an endless number of possible intervals that one can experiment with (I'll provide some examples further on).

The next question after "What is HIIT?" is usually, "Does it work?" Again, the answer is yes.

Martin Gibala, Ph.D., a professor of kinesiology at McMaster University in Hamilton, Ontario has dedicated more than a decade to studying the effect of brief, intense interval exercise and has put his research into practice by designing time-efficient workouts. He compiled much of this in his book “The One-Minute Workout”, published in 2017.

An example of this research is a study that compared how effective a 10-minute workout could be compared to a 50-minute session. In this study, a group of sedentary men were separated into two groups and performed three training sessions per week for a total of twelve weeks. The first group's protocol consisted of 3 x 20 seconds “all-out” cycling efforts separated by 2 minutes of low-intensity cycling. The second group's protocol consisted of 45 minutes of continuous cycling at moderate intensity. Both protocols included a warm-up and cool-down totaling five minutes. The results showed that peak oxygen uptake and other indices of cardiometabolic health improved to the same extent in both groups despite the difference in exercise volume and time commitment.

It is important to remember that the study was conducted on sedentary but otherwise healthy individuals. Gibala and his co-authors also noted, in the paper outlining the research, that training protocols that involve high intensity effort are not suitable for everyone--cardiac patients, for example.

The takeaway from this study--and from many others that have been conducted on HIIT--is not that we can spend a minute a day exercising and reach peak health and fitness. Rather, it is that a high percentage of the benefits typically associated with prolonged steady-state endurance training can be gained with less time than first thought. Just like strength training, effective cardiovascular training doesn't require hours a day, seven days of the week. HIIT protocols can be used to create time-efficient training sessions that deliver numerous health benefits.

Some critics of HIIT argue that what stops people from working out is not always lack of time, but the unpleasantness of experience that comes from such intense intervals. But for every person put off by intense exercise there are multiple that are thrilled to be able to complete an effective workout in less than thirty minutes and willing to take on and conquer the challenge that HIIT presents.


One thing to keep in mind before we move onto some example workouts is this: HIIT, done properly, is hard. If it is to work it requires the person undertaking it to get out of their comfort zone and expend effort at a level close to their limit. But how do we measure the intensity of an effort? It is possible to track oxygen consumption using fancy equipment. It is simpler to monitor heart rate using one of the ubiquitous HR monitors available to the public. But it's simplest to use the RPE (rate of perceived exertion) scale. The RPE scale goes from 0 to 10, the former indicating no exertion at all, and the latter indicating maximal effort. Here's a handy table which describes the scale.

As you can see the RPE scale is personal and subjective. It's self-reported, which means that your notion of a seven could be different from someone else's. But most people, given the 0-10 scale, agree on what a 0 and a 10 are and can place themselves relatively accurately.


Before we look at some examples of HIIT sessions, a recommendation: check with your physician before starting a new exercise routine, especially if you have any pre-existing medical conditions.

With that out of the way, here a few tips for people new to HIIT programs:

- Start with easy workouts and move gradually to more intense workouts.

- Generally, a workout with shorter intervals and more cycles will be easier than the reverse.

- Recovery between intervals has to be active. Do not go from all-out activity to a complete stop.

- Start each session with a few minutes warm-up and finish with a few minutes of cool-down.

- Remember, 15-30 minutes a few times a week is all you need to get started.

- Don’t forget to celebrate small wins. Each workout is a step towards better health.

- HIIT training offers more immediate benefits to beginner practitioners than it does to advanced practitioners.

Finally, here are a few general points about HIIT that are worth keeping in mind:

- Since HIIT can elevate your heart rate to around 90% of your maximum, governing bodies are holding back on officially advocating these protocols to the public. They are waiting for more comprehensive data on its long-term effectiveness and safety for different populations. That shouldn't stop you though--official policy and legislation typically lags years, and sometimes decades, behind established best-practices.

- We know the physical decline of the body with age is inevitable but getting older does not mean getting weaker or more sedentary. With the exception of those whose health makes intense exercise dangerous, HIIT can be implemented as part of anyone's weekly routine.

- For decades people with certain chronic conditions were advised not to exercise at all. Now scientists and doctors know that far more people can and should exercise, and even very vigorous exercise like HIIT can be appropriate for people with chronic conditions like Type 2 diabetes and some heart conditions. It even has benefits for cardiometabolic and brain health . HIIT can be safe for people at different fitness levels as long as they adjust the definitions of "intensive" and "all-out" to fit the constraints of their bodies.

Now, onto the example sessions.


HIIT can make use of any sort of exercise, not just running, cycling, swimming and other aerobic activities. It can also include elements that target different physiological systems. For example, bodyweight-style movements like burpees, push-ups and pull-ups, or other strength and resistance training exercises that make use of kettlebells or weights. Performing these exercises at speed tests not only the aerobic system, but the muscles and joints involved as well. Keep that in mind when considering these two example workouts from Martin Gibala's "The One-Minute Workout". Both are measured using the RPE scale.

- "The Basic Training Workout"

Peak Intensity: 7 RPE

Total Duration: 30 minutes

Who's It For? Healthy people in the early to middle stages of training who are looking to break through performance plateaus or quickly boost their cardiorespiratory fitness.

The Workout:

1. Warm up with a very light activity at an intensity of 1 or 2 RPE for 3 minutes.

2. Increase the activity to a level of 7 RPE (breathing should be rapid, forceful, and you should be unable to talk). Maintain it for 3 minutes.

3. Active rest at 2-3 RPE for 3 minutes.

4. Repeat intervals of 3 minutes on, 3 minutes off for 5 total cycles.

- "The Ten by One"

Peak Intensity: 9 RPE

Duration: 25 minutes

Who's It For? Anyone healthy enough to undertake intense exercise.

The Workout:

1. Warm up with light activity at an intensity of 1 or 2 RPE for 3 minutes.

2. Conduct your first sprint at an intensity of 5 RPE for 1 minute.

3. Conduct 1 minute of recovery at an RPE of 2 or 3.

4. Complete a second sprint for 1 minute at an RPE slightly above the previous sprint.

5. Conduct 1 minute of recovery at an RPE of 2 or 3.

6. Continue the cycle with gradually increasing sprint RPE until you've done 10 sprints in total, the last culminating in a near-max effort.

7. Cool down with several minutes of low-intensity activity.

There are endless examples of sessions that I could list here, and I encourage you to experiment with your own. But keep this in mind:

- HIIT typically cycles between low RPE activity and high RPE activity. 1+9, 2+8, 3+7, etc. The sessions are typically quicker too, as the effort expended is much greater in a shorter period of time.

- Regular interval training cycles between activity of similar RPEs. 3+5, 4+6, etc. Regular interval training usually involves longer intervals for longer durations.

- A good rule of thumb when crafting your own session is to make sure the intervals add up to 10 or 11 on the RPE scale. Less than that will be too easy. More than that will be too hard.


The best exercise programs are the ones we can do and want to do regularly and consistently. Some people don't mind spending hours on rigorous and exhaustive programs. But many of us also like something shorter, sweeter and more challenging. HIIT offers an alternative to traditional programs, and it offers an opportunity for those discouraged by conventional training. Try it.

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