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High Intensity Training | Everything You Need To Know

A fitness enthusiast completing a HIT workout.

If you want to discover the benefits of high intensity training (also known as HIT), and how to apply it to your workouts, you’ve come to the right place. In this article, we will explore the many fascinating ways that HIT can improve your fitness and health.

In addition, we will look at the fundamental features that distinguish high intensity from other training methods. By the end of this article, you’ll have a grounded understanding of this essential training principle.

Plus, you’ll know how to reformat your workouts so that they tick the high intensity training box. And, finally, you’ll have access to many relevant publications that explore the subject in more detail.

So, first things first, . . .

What’s high intensity training?

Simply stated, high intensity training refers to the level of effort required to exceed your normal exercise output. How intensity is expressed, though, differs depending on the training method.

For example, an endurance athlete would be training at high intensity when their heart rate is above 50% of its maximum capacity.

A simple method of establishing heart rate training zones is to deduct your age from 220. ‘Using this formula an 80 per cent training intensity for a 30-year-old male is 152 beats per minute,’ (Physical Fitness & Athletic Performance).

One-rep max (1RM)

In contrast to aerobic training, a power-strength athlete or ‘strongman’ will judge intensity against pre-established maximal lifts. For a powerlifter to train at a high intensity, they would have to lift at least 80% to 85% of their one-rep max (1RM) (NSCA’s Guide to Program Design). As an example, if your 1RM deadlift is 100kg, a high intensity lift for you is a load above 80kg.

Judging high intensity during a circuit is not so straightforward. Instead of using physiological biomarkers (heart rate) or personal bests (one-repetition max), participants in a circuit could assess their output against a recognised intensity scale.

Alternatively, depending on the organisation of the circuit, they could use a mixture of heart rate and maximal lifts.

How hard should I exercise during a high intensity training?

A common misunderstanding is that you must maintain maximum output during a high intensity workout. Of course, it’s not physically possible to sustain 100% effort for any more than a few seconds.

But a high intensity workout doesn’t require that you push yourself to the limit. Instead, you need only exercise at an intensity that’s noticeable above what you normally train at.

Watson makes the same point when he reminds us that the ‘critical intensity’ – i.e., the percentage of heart rate max that resides within side the high intensity training zone – ‘seems to be a level greater than that which the subject normally experiences,’ (Physical Fitness & Athletic Performance).

High intensity doesn’t mean 100% effort

Watson supports his suggestion by citing studies that report gains in aerobic capacity ‘following exercise between 120 and 135 beats per minute.’ Translated to output, 120 to 135 beats roughly equate to 50% max effort. This shows that fitness levels can be improved without having to push yourself to the point of exhaustion.

Edmund Burk PhD., who is a world-renowned athletic performance coach, advances a different approach to intensity training. He advises that we ‘gradually raise’ our heart rate close to the lactate threshold over the duration of the interval or workout (Serious Cycling – Second Edition).

Sustaining output near the lactate threshold would certainly constitute high intensity. However, few people possess an understanding of their heart rate training zones. Using the formula above can provide a simplified method of ascertaining that information.

Easier ways of judging training intensity include using Grantham’s 5-Level Scale or Borg’s Rate of Perceived Exertion (RPE) scale.

How do I go from low to high intensity training

Let’s say that your typical gym session consists of 45 minutes of resistance exercise organised around the sets-reps-rest formula. Throughout your routine, you barely break a sweat, and your heart rate remains at a steady seventy-five beats per minute. This is your normal exercise experience.

To turn up the intensity, to trigger the ‘critical intensity’, you could simply reduce the rest periods between sets. Subtle those this modification is, you’d instantly feel the difference: your heart rate would quickly climb, and your muscles would begin to burn.

High-intensity training tool kit

Training experience and trying out different HIT Workouts will enable you to build a high intensity training tool kit. This tool kit is essentially a stock of methods that you can use to vary the intensity of your workouts.

For example, you can manipulate training intensity by increasing loads, pushing to failure, including a power element to exercises (such as a plyometric jump at the end of a squat), or speeding up the reps.

In addition, heart rate monitors and other exercise technology offer novel methods of measuring training intensity. For example, the Polar Vantage sports watch provides the wearer with instant feedback on their current training zone.

How high is high intensity training?

Another point of note concerning HIT is brought to our attention in the book The Strength & Conditioning Bible. Performance Enhancement Specialist, Nick Grantham, tells us ‘always to remember the ‘individual differences’ cornerstone and consider other factors that can impact on training intensity’ (such as age, fitness goals, and exercise experience).

In essence, what’s being alluded to here is the broad variety of individual physical abilities. A beginner’s experience of high-intensity training will differ markedly from an athlete, as would a 22-year-old’s to that of a septuagenarian.

To help us judge training intensity, Grantham outlines a simplified five-point scale that we can apply to our workouts.

HIT scale

  1. Level One: No Fatigue – very easy, walking, or the initial phase of a warm-up.

  2. Level Two: Medium Fatigue – still easy but feeling the physiological systems respond: slight increase in heart rate; equivalent to an upbeat jog.

  3. Level Three: High Fatigue – feeling challenged; heart rate is up and sweating profusely; equivalent to running with purpose.

  4. Level Four: At the point of Failure – incapable of sustaining output for more than a few minutes; sprinting.

  5. Level Five: Beyond Failure – at the point of collapse or require assistance during a lift.

The scale offers an accessible insight into a recognisable range of intensity indicators. Furthermore, its simplicity does away with the need to establish a personalised intensity measure based on the Borg Rating of Perceived Exertion (RPE).

At glance, you could quite easily rate your exercise intensity against the five levels. This method of monitoring intensity is more suited to circuits and gym workouts.

How much high intensity training per week?

In short, not much. Training at a high intensity too frequently increases injury risk, burn out, and can result in ‘reversibility.’ Reversibility, if you’re unfamiliar with the term, refers to the decline in fitness caused by, among other reasons, not giving our body adequate time to recover between workouts.

It’s for these reasons that HIT should be sprinkled lightly over your routine. You have a couple of options for how to do this.

Option 1: Implement a designated high intensity training day. On the said day you would modify your current workout (applying the suggestions above) or replace it with something similar to the one below.

Option 2: Conclude each of your weekly workouts with a high intensity finisher. What would this look like? After sauntering through your obligatory Monday back and biceps workout, you would bolt on this blistering cardio scorcher or this kettlebell snatch AMRAP.

High intensity training vs volume

High intensity training and volume are often confused. It’s easy to understand why. After all, working harder throughout a session means that we get more done. And getting more done suggests greater volume.

However, there are a few subtle differences that distinguish these two training variables.

Intensity is about the level of effort invested in a workout whereas volume ‘means the amount of work carried out in a particular training period or session,’ (The Complete Guide To Sports Training). Reflecting back on the opening question, intensity is expressed by a percentage of either your maximum heart rate or one-repetition max.

Volume, in contrast, is measured in ‘terms of time, numbers of repetitions or ground contacts […] or the amount of weight lifted’ over the course of a workout. But while intensity is measured during a single workout or workout segment, volume can include the amount of training completed over a week, month, or year.

Is high intensity training bad for you?

There are scores of studies showing a strong relationship between HIT and improved physical performance. Depending on you apply intensity in your workouts, it can improve cardio capacity, muscle endurance, strength, and power.

The benefits of intensity training don’t stop at improving components of fitness. Driver (2017) states that high intensity training ‘is now increasingly being prescribed by doctors to patients with all manner of conditions and ailments,’ (HIIT: High Intensity Interval Training).

Factoring intensity variations into your workouts can confer a multitude of benefits. Some of these benefits include:

Improved physical performance
Improve muscle tonality
Promoting rapid weight loss
Reduce disease risk
Increase exercise enjoyment

However, while HIT boasts a broad range of benefits, it can be bad for certain people. For example, those with a heart condition, hypertension, or atherosclerosis would be wise to avoid high intensity training. The sudden increase in stroke volume (the amount of blood pumped out of the heart with each beat) could result in cardiac complications.

Other factors that put people at risk during high-intensity training include being overweight or obese, elderly, untrained, or injured. To err on the side of caution, anyone that falls in one of those categories ought to speak with their doctor before engaging in high intensity training.

What’s high intensity workout?

For a workout to qualify as a ‘high intensity’ it would have to fulfil those requirements outlined in the first question (What’s High Intensity Training?). If you planned to participate in 30 minutes of aerobic exercise, your heart rate would at a minimum have to exceed 50% of max effort for all or part of the duration.

Likewise with a resistance workout. The loads selected would have to be at or above 80% of your one-repetition max. Though it is worth bearing in mind that these percentages are not an absolute prerequisite for the promotion of strength gains. In ‘untrained athletes’ intensities of 45% to 50% of 1RM or less ‘may increase muscle strength,’ NSCA’s Guide to Program Design).

Follow the link for an example of a HIT workout.


This blog on HIT concludes with the author bio.



Driver, J (2012) HIIT: High Intensity Interval Training. CreateSpace Independent Publishing. UK.

Grantham, N (2015) The Strength & Conditioning Bible. Bloomsbury. USA.

McArdle, W. D., Katch, F. I., Katch, V. L (2001) Exercise Physiology Fifth Edition. Lippincott, Williams & Wilkins.

Shepherd, J (2006) The Complete Guide To Sports Training. A&C Black. London.

Watson A. W. S (1995) Physical Fitness & Athletic Performance. Longman. England.

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