4 Amazing, Unexpected Benefits of HIIT That You Probably Don’t Know

Work as hard as you can for a short while, take a fast break, repeat. That’s high-intensity interval training, HIIT, in a nutshell. It’s a simple idea with amazing results.  Some of them may surprise you.

Amazing results have been the promise of HIIT from the beginning, when it started as a little-known technique to improve runners peak performance. One of the earliest backers, coach Peter Coe trained his son Sebastian with intervals because he believed that “long, slow distance running creates long, slow runners.”  

Using the intervals his father devised, Sebastian’s training led him to set three world records in 41 days in 1979. By the next year, Coe held three middle distance world records---  800m, 1000m, 1500m. He actually set a new record for the mile and simultaneously held all four world middle distance records for an hour, until another runner bested him in the mile.      

Now, what’s amazing is what HIIT can do for you whether you ever go for a run or not. Whether you’re an athlete or bare beginner, you are in for some rewards with HIIT.

Ask Doc for Clearance

During the intense intervals of HIIT training, you need to exert your maximum effort. So check with your doctor if you have any health concerns before you start a HIIT workout.  In the last few years, there has been new research finding it’s even beneficial for patients recovering from heart disease. But obviously that is something to work out with your personal physician.

You can find reams of studies and hundreds of online articles that will explain the usually touted benefits of HIIT. Yes, it can


  • reduce blood pressure
  • improve blood glucose
  • increase VO2 Max
  • slightly raise your metabolic rate for longer after a workout
  • help you lose weight

That said, here’s what else HIIT could do for you.

1. Burn significantly more absolute fat mass in 75% less time

In 2019, review of 786 papers on HIIT found 36 very high quality studies that documents changes in fat mass. These trials lasted at least four weeks and compared results from interval training with traditional aerobic exercise.  

The results were consistent and unequivocal.  Compared to regular aerobic exercise, people who followed a HIIT regime lost 28.5% more fat mass.  

This means HIIT really reduces fat. It doesn’t just make fat a lower percentage because of adding muscle. Nor is it losing fat proportionally along with water and muscle tissue as your total weight drops. This takes the lard off! You couldn’t ask for better results.

That’s stunning and a good reason to devote 40 minutes a week (or less) to HIIT instead of putting in the usual recommended 150 minute per week minimum for aerobic exercise.

2. Feed Your Brain

With all the focus on body, muscles, fat and energy there’s another benefit that gets less attention and should matter a great deal to you. HIIT speeds up oxygen delivery and blood flow. That creates more fresh supplies to the brain, the most oxygen-hungry organ in your body.

3. Increase Your Stamina and Presence


We often concentrate on physical measures and forget what their real effect is.

If you go through life tired, your low energy affects how people see you. It’s a negative impression. But if you have more energy, you glow, you get more done, you are more alert, and you impress people much more positively. Put simply, you have more presence.

That’s what makes the increase in stamina from HIIT a life changer. HIIT increases your endurance by boosting the energy in cell mitochondria. For athletes, this can mean the ability to run longer, but for all of us, it translates into more alert, useable energy every day.

4. Make Heart, Artery and Veins More Flexible

Sure, HIIT increases aerobic capacity. Everyone knows that. But HIIT also improves the flexibility and elasticity of heart and blood vessels. This is especially true for people who are over 30, the age at which these vessels begin to become stiffer in most people.

In addition to this direct effect of HIIT on cardiovascular health, it lowers blood pressure. High blood pressure speeds up the pace of elastin degradation, which makes blood vessels stiffer and less healthy. HIIT can reverse that, especially along with other changes like a diet rich in fish oil, fruits and vegetables.

5. Increase HGH, testosterone and insulin-like growth factor 1

For men and women, HIIT has been found to increase insulin-like growth factor 1 (ILGF1) and growth hormone. For men, but not women, it increases testosterone.  All these are involved in muscle and tissue repair and in helping your body stay younger for longer.

But to get the most of all these benefits, you have to do within bounds, not too much.

Photo credit: Julia Larson

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