What are the benefits of high intensity interval training (HIIT)?

HIIT is any form of exercise that consists of a short burst of intense exercise that precedes a period of rest or low intensity exercise.

The period of intense exercise can vary from less than 45 seconds to a few minutes. People then rest or do gentle exercise for a similar time frame before repeating the sequence.

An entire HIIT workout may be as short as 15–20 minutes, but it provides a wide range of benefits. Its short duration can make it a very practical and effective choice for people who find it difficult to commit to longer sessions.

HIIT also requires no equipment or gym membership, so people can do it anywhere at a time that suits them.

Research suggests that HIIT workouts may be better than moderate intensity exercise for “maximizing health outcomes.”

HIIT offers many benefits, including:

Reducing body fat

According to a 2012 study, HIIT may decrease body fat more than steadier types of exercise, such as jogging.

The study looked at the effects of HIIT on 46 males with overweight. The participants, who had an average age of 25 years, took part in three 20-minute HIIT sessions a week.

After 12 weeks, those in the exercise group had a significant decrease in abdominal fat compared with those in the control group.

A more recent study found that HIIT workouts using a hydraulic resistance system may burn more calories than equal periods of steadier forms of exercise. These findings suggest that HIIT may help people burn more calories in less time.

Improving cardiovascular and metabolic health

HIIT may help improve heart health in people with good health, as well as in those with cardiovascular conditions.

It may also help improve measures of metabolic health, including blood pressure, blood sugar levels, and cholesterol.

A 2015 study found that a 10 week program of HIIT workouts produced cardiovascular and metabolic benefits that were similar to those of moderate intensity workouts.

In the study, 90 participants who were previously physical inactive completed either a HIIT program or a traditional moderate intensity continuous training (MICT) program. The average total exercise time of 55 minutes per week for the HIIT program was less than half of that for the MICT, which took the participants an average of 128 minutes per week.

Improving mental health

Although all exercise may benefit mental health, HIIT training may be especially helpful.

The authors of a 2019 review suggest that HIIT can provide a range of benefits for people with mental illnesses, including reducing the severity of depression.

Although the review looked at 12 studies, the authors stated a need for further high quality trials to support these findings.

A 2015 study looked at the effects of HIIT training on people with chronic schizophrenia. The research found that many people with psychiatric conditions had low motivation to exercise and felt that exercise was too time consuming.

Short HIIT workouts could help overcome difficulties with motivation and finding time to exercise. The study recorded the effects of an 8 week program of HIIT workouts in people from a psychiatric day care unit.

The program consisted of three workouts a week, each of which was 15 minutes long with 5 minutes warming up and cooling down either side.

Of the 20 participants, 18 completed the program. The results showed the following mental and physical improvements:

• decreased body mass index (BMI)
• lower resting heart rate
• lower pulse pressure
• decreased body weight
• improved mental health scores, including reduced levels of depression and social avoidance

Time efficient

Despite the benefits of exercise, not everyone is keen or able to commit to regular sessions. One of the most common barriers is a lack of time.

HIIT is an efficient way to exercise, and it may, therefore, be a good choice for people who find it difficult to fit physical activity into their schedule.

According to a 2014 study, a commitment of just 30 minutes three times a week could be beneficial.

The researchers found that each of these 30 minute sessions had to include just 10 minutes of intense exercise for the person to gain the following benefits:

• improved heart and lung health
• improved metabolic health, which includes cholesterol and blood pressure levels
• increased oxygen supply to the muscles
• improved exercise tolerance, which is how well the heart responds to exercise

Researchers saw these benefits after just a few weeks in both healthy participants and those with cardio and metabolic conditions.

One of the benefits of HIIT is that people can do it anywhere, including at home or in a park.

Although there are likely to be HIIT classes on offer at a local gym, no classes or equipment are necessary for this type of training.

People can use their preferred form of exercise for the exercise intervals. They may wish to cycle, sprint, or use a skipping rope. If a person is using exercise equipment, they can increase the resistance for extra intensity and then reduce it again for the rest period.

People can also do a variety of exercises using just their body weight, such as:

• pressups
• burpees
• jumping jacks
• squats
• situps

An example of a 25-minute HIIT workout is as follows:

• 5-minute warmup
• 15-minute HIIT circuit:
  • intense exercise for 15 seconds
  • rest 10 seconds
  • intense exercise for 15 seconds
  • rest 20 seconds
  • intense exercise for 15 seconds
  • rest 30 seconds
  • intense exercise for 15 seconds
  • rest 40 seconds
  • intense exercise for 15 seconds
  • rest 50 seconds
• Repeat this circuit three more times
• 5-minute stretching session to cool down

People can either stop exercising in the rest periods or switch to gentle exercise, such as walking or slow cycling.

Many people may find that they are not meeting the recommended 150 minutes of moderate exercise each week.

There can be a variety of reasons for this, but a lack of time is a common barrier. Not getting enough regular exercise can increase the risk of certain health conditions.

HIIT involves interspersing short bursts of intense exercise with rest periods. The intensity of the exercise means that HIIT sessions can be as short as 15–30 minutes but provide equal or superior benefits in comparison with longer periods of moderate intensity exercise.

HIIT requires no equipment, so people can do a workout at home or in a park at a time that suits them best.

Research has found that HIIT workouts may help improve cardiovascular and metabolic health, decrease body fat, and improve mental health.