In the ‘80s, it was aerobics. In the ‘90s, racquetball. What exercise craze made its landing in the 2000s? HIIT. In fact, since 2004, researchers from fields ranging from kinesiology to cognitive neuroscience have been studying the power of this workout style and its incredible health benefits.^1,2 And no, HIIT isn’t just for people training for an event or trying to hit a weight loss goal. Have we piqued your interest? Keep reading.

What is HIIT?

High Intensity Interval Training, a.k.a. HIIT (spoken “hit”), is a type of exercise characterized by intermittent periods of strenuous, all-out work (“high intensity”) coupled with low-intensity active recovery periods.

In the fitness community, it’s widely regarded as one of the most efficient methods for improving cardio fitness and metabolic function.

If it sounds tough, that’s because it is. But HIIT isn’t just for top-tier athletes anymore; research from the past decade or so shows that HIIT has pretty impressive effects on markers of general health and wellness.³

And while the thought of pushing yourself to your physical limit can seem, well, nauseating for some people, there’s a pretty sweet trade-off: it requires very little of your time. In fact, a study published in 2014 found that a one minute HIIT workout performed three times a week for 18 weeks improved markers of heart health like VO2 max and systolic blood pressure as well as those of glucose metabolism like insulin sensitivity.⁴

Bottom line: if you have a few spare minutes, you have the opportunity to improve your long-term health. Now, let’s get a little further into these physiological effects.

How HIIT can benefit blood test results

We regularly recommend HIIT for InsideTracker Action Plans. Here’s why.

Increases low folate

Researchers found that HIIT training increased folate levels in teenage swimmers, but that after returning to a volume-based regimen (like hitting a weekly mileage goal), folate levels returned to baseline.⁵ Moral of the story: this is a lifestyle change, not a one-and-done task.

Increases low free testosterone

Research has shown that, in male runners, interval training increases free testosterone more than steady-state runs.⁶ So, if your free T has been low, or you’ve been feeling the beginning phases of over-training, try bumping your mileage down and switching out some steady, long runs for intervals. Need a workout suggestion? We’ll get there...

Improves lipid biomarkers

If your lipid group hasn’t seen the Optimized Zone in a while, try interval training. A study found that healthy adults who, on average, spent 55 minutes a week of HIIT had more significant improvements in HDL, LDL, total cholesterol, and triglycerides than a group who averaged 128 minutes of steady state work in the same time frame.⁷ In case you were wondering, 55 minutes a week averages out to less than 8 minutes a day. That’s almost exactly the amount of time a 30-minute TV show spends on commercial breaks. Catch our drift?

Looking specifically to boost HDL? In one study, young men who ran just two miles interval-style (800m max intensity, 800m active rest) three times a week experienced significant increases in HDL. For what it’s worth, they also reduced their 1.5 mile time.⁸ New PR, here you come!

Reduces liver enzymes

Liver enzymes typically rise when we consume inflammatory substances like alcohol or gluten (specifically in Celiac warriors), or battle an infection. And if your AST or ALT is higher than optimal, HIIT could be your cure: one study showed that intervals of about two minutes of high-intensity work paired with three minutes of rest for 30-40 minutes three times per week significantly reduced both enzymes.⁹ So if you partied a little too hard, show your liver some love with this pattern in the following days.

Try these HIIT workouts

There are many different styles of HIIT practiced all over the world. Tabata, named after the researcher that founded the method, is a type of HIIT characterized by its repeated rounds of 20 seconds of work paired with 10 seconds of rest for eight rounds, totaling four minutes. Studies by Tabata and his research group have found these four minutes of work to be as beneficial for heart health as an hour of steady-state exercise such as running.¹⁰ Other notable HIIT patterns include:

• 30 seconds on, 10 seconds off for 6 rounds
• Ascending intervals starting with 20 seconds for five rounds up to 60 seconds of work, with 10 second rests in between
• Descending intervals of the same nature, starting at 60 seconds
• Push-push pause: 30 seconds of work with 10 seconds of all-out effort, followed by a 10-second break for 4 rounds
• Gladiator-style: 90 seconds of work paired with 45 second breaks for 5 rounds

If you like to cross-train/circuit train, try:

• Alternating 20 second rounds of high knees and tuck jumps with 10 second breaks for 8 rounds
• 30 seconds of squat jumps, 10 second squat hold, 10 second rest for 4 rounds
• Punching a bag for 20, 30, 40, 50, and 60 seconds with 10 second rests in between

If you like to run, try:

• Sprinting for 30 seconds, jogging for 60 for 10 rounds
• Sprinting up a hill and walking down for 8 rounds

If you like to swim, try:

• Sprinting 1 length, active recovery 1 length for 4 laps
• Sprinting 30 seconds, resting 30 seconds for 2 laps

If you like to bike, try:

• Sprinting for 20 seconds, resting for 10 seconds for 2 miles
• Sprinting the space between 3 telephone poles, resting for 5 lengths for 10 minutes

 If you’re intimidated by the intensity of HIIT, try starting with just a few rounds at 100% effort rather than all rounds at a weaker effort. This will help get your body used to the intensity and build strength.

The takeaway

If you’re trying to reach a new fitness goal or lose some weight, HIIT is definitely a tool you should keep in your belt. But this method isn’t just for people with a specific endgame in mind! Incorporating HIIT into your regimen 1-3 times per week can help you build a strong body and heart for a long, healthy life.