Lack of time is often the main reason people don’t exercise regularly. But a type of interval workout recently popularized by actress Jessica Biel could be the solution – with research showing it can improve fitness faster than traditional, steady-pace workouts, such as jogging or cycling.

The Norwegian 4×4 workout has traditionally been used by athletes. It’s a form of high-intensity interval training (Hiit) that involves four-minute sets of very intense cardio exercise, followed by three minutes of very light exercise.

A typical training session includes a five-minute warm-up, four high-intensity intervals and a five-minute cool-down.

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The 4×4 workout format follows the same format as other Hiit workouts, which alternate periods of high-intensity exercise with periods low-intensity exercise (or rest). Most Hiit workouts involve work intervals that last anything from ten seconds up to a couple of minutes. In contrast, the 4×4 workout employs four minute work periods, which raises your heart rate for longer than most Hiit protocols.

Decades of research has shown that regular Hiit workouts are often more effective than moderate-intensity workouts (such as running or cycling at a steady pace continuously) in improving cardiovascular fitness and other health outcomes (such as improving blood sugar and cholesterol levels). Hiit is even effective for improving health in adults with type 2 diabetes and cardiovascular disease.

Hiit also offers these benefits with less training time than traditional endurance training. A 2008 study showed that as few as six Hiit sessions over two weeks improved the muscles’ endurance capacity.

Several studies have also explored the benefits of the 4×4 protocol. For example, an eight-week study showed that the 4×4 workout produced greater aerobic fitness improvements than 45-minute moderate-intensity running sessions.

The reason the 4×4 workout specifically is so effective for improving cardiovascular fitness is because the four-minute intervals are intense enough to maximally challenge your heart and lungs while minimizing muscle fatigue. This helps improve your maximum oxygen uptake (or VO₂ max), which is the highest rate at which your body can take in, transport and use oxygen during intense exercise.

VO2 max is considered the gold standard measure of cardiovascular fitness. Higher VO₂ max values are associated with reduced risk of cardiovascular disease and premature death, and better overall health.

During a 4×4 workout you’ll spend roughly 16 minutes close to you maximum heart rate. This means that it can improve VO2 max more effectively than longer duration, moderate-intensity workouts.

Choosing the right workout

For people with busy schedules, Hiit is a time-efficient option because it offers the same health and fitness benefits as longer workouts with less training time. However, a 4×4 Hiit session still lasts between 35–40 minutes, which might be too long for some people.

For those seeking a shorter workout option, the 10×1 Hiit protocol is a suitable alternative as it can be completed in just 30 minutes – including warm-up and cool-down periods.

This involves doing ten one-minute intervals of intense exercise. Each minute of hard work is followed by a minute of light exercise or complete rest.

But while this protocol also improves VO₂ max, the shorter work periods must be performed at a much higher intensity than the four-minute intervals to challenge the cardiovascular system. This could make it difficult to pace yourself consistently during each interval.

Another Hiit workout option is sprint interval training. This involves exercising as hard as possible for ten to 20 seconds – followed by three minutes of recovery. These sprints can be done running, cycling or even rowing.

One 12-week study found that participants who performed three, 20-second sprints (followed by three-minute recovery periods) just three times a week significantly improved their cardiovascular fitness compared to those doing longer, steady-state workouts.

However, the 4×4 workout has been shown to produce better gains in aerobic fitness than sprint interval training.

Although most research shows that Hiit produces rapid health and fitness benefits, it’s difficult to know exactly how effective it is in the real world because most studies use specialized equipment and are supervised by researchers. As such, study results may not reflect what happens when people train on their own.

The very demanding nature of Hiit may also make it less enjoyable for some people – particularly those who aren’t used to intense exercise. This is important, because lower enjoyment is linked to poorer motivation and lower likelihood of sticking to a workout program.

Also, while Hiit is often promoted as exciting and time efficient, its novelty may wear off. What feels new and motivating at the start may become tiring or repetitive, especially without variety or support. As a result, some people may struggle to stick with a workout program after a few weeks.

Long-term fitness improvements come from training consistently. For that reason, it’s essential to choose a form of exercise that you enjoy.

If Hiit is less appealing to you than alternatives, such as steady jogging, cycling or weightlifting, it may be more effective to focus on workouts you’re more likely to stick with.

You don’t always have to push yourself to the limit to improve your health and fitness. Even consistent activity, such as accumulating around 7,000 steps a day, can still lead to meaningful physical and mental health benefits.

The Norwegian 4×4 protocol is just the latest popular Hiit workout. While it can offer many health and fitness benefits for you in a short period of time, it might not suit your needs – so be sure to pick a workout that best suits your goals and schedule.

Paul Hough, Lecturer Sport & Exercise Physiology , University of Westminster

This article is republished from The Conversation under a Creative Commons license. Read the original article.