Think you don’t have enough time to exercise? Join the club. Among the reasons people cite when asked why they don’t work out, lack of time comes out on top. (1)

The U.S. Department of Health and Human Services recommends that adults get between 150 and 300 minutes per week of moderate-intensity exercise per week. However, you can cut that time commitment in half by opting for high-intensity workouts instead. (2)

One proven way to reap all the benefits of exercise in less time is with high-intensity interval training (HIIT). Research shows that spending less time doing HIIT may even be better for you than spending more time doing less intense exercises.

What is high-intensity interval training (HIIT)?

High-intensity interval training alternates explosive bursts of full-throttle effort with periods of recovery—through either rest or lower-intensity exercise. In fitness centers and gyms, HIIT often includes both cardio and resistance training, but HIIT can also be done as strictly a cardio routine.

man measuring his heartbeat on neck

HIIT often includes both cardio and resistance training. You can wear a heart rate monitor to keep track of how much you’re exerting yourself while working out.

During your intense bursts, you’re working at around 80 percent of your max heart rate for a period of 15 seconds to a few minutes. Between each of those periods, you’re either slowing down or resting completely to let your heart rate come back down to around 50 percent of maximum.

You can calculate these different target heart rates by using an online calculator. (13) Then during your workouts, you can wear a heart rate monitor to keep track of how much you’re exerting yourself.

For a lower-tech option, Denver-based certified personal trainer Lindsay Kelly, NASM, recommends what she calls the “talk test.”

When you’re at your target intensity heart rate—when you’re sprinting, for example—it should be hard to speak more than two words without taking a breath. Then when you’re in the recovery period, the reverse is true.

Expert insight

“If you can’t say more than two words, then you still need to recover,” Kelly says. “That way, you have the full recovery to be able to push your body to that intense level again.”

Why high-intensity interval training works

HIIT is so effective because it allows you to exercise at a higher intensity than you otherwise could since you’re doing it for such short periods. This exertion gets your heart working and your blood pumping better than more prolonged periods of moderate-intensity exercise can.

Expert insight

“HIIT is great for maximizing your amount of work in a short time,” Kelly says. “It feels like a mental challenge. If you tell yourself you have 60 minutes to work out, you’re going to slip up at some point and not give it your all. If you tell yourself you only have 10 or 20 minutes, then you really push yourself.”

Importance of rest

While you might not realize it, the rest periods built into HIIT are a critical part of the routine. They force your body to adjust to a very different state of activity, which is great for cardiovascular conditioning.

Feel the afterburn

Another benefit of HIIT is that even after you’ve finished your workout, it keeps on working for you. Research shows that you keep on burning calories after your HIIT workout at a higher rate than you would after a continuous exertion workout. (3) It’s commonly referred to as the “afterburn effect,” and it helps you extend the benefits of your efforts.

The scientific basis for high-intensity interval training

According to a paper in the journal Applied Physiology, Nutrition, and Metabolism, “As little as 3 HIIT sessions per week, involving ≤10 min of intense exercise within a time commitment of ≤30 min per session, including warm-up, recovery between intervals and cool down, has been shown to improve aerobic capacity, skeletal muscle oxidative capacity, exercise tolerance and markers of disease risk after only a few weeks in both healthy individuals and people with cardiometabolic disorders.” (4)

Let’s explore the science behind the widespread enthusiasm for HIIT.

High-intensity interval training benefits

High-intensity interval training has been studied extensively, and the results are clear: HIIT is better than continuous exercise at improving health in a variety of ways.

One of the health benefits of high-intensity interval training is that it improves cardiorespiratory fitness (that’s the health of the heart and breathing). Why does that matter? Because cardiorespiratory fitness is a primary factor in the risk of disease and death.

A review of 10 different studies on the topic found that HIIT increases cardiorespiratory fitness at twice the rate of continuous exercises. (5)

And the health benefits of high-intensity interval training don’t stop there. Other research has shown that it can help with the following areas of health as well.

woman running outdoors

HIIT is better than continuous exercise at improving health in a variety of ways including building your endurance and stamina.


By improving cardiorespiratory fitness, HIIT improves your stamina. It does that by enhancing your body’s ability to consume and use oxygen. One large review study compared standard endurance training to HIIT by looking at how they affected maximal oxygen consumption, known as VO2max. The researchers found that HIIT was superior to endurance training in improving VO2max in healthy young to middle-aged adults. (6)

Once you start to build your endurance, you can increase the length and/or intensity of the working periods, and then you’ll enjoy even more significant health benefits from HIIT. (7)

Heart health

High blood pressure is a major contributor to cardiovascular disease and death. (8) One of the best ways to keep blood pressure in check is through regular exercise.

The traditional recommendation for blood pressure modulating exercise has been to exercise at moderate intensity for 30 minutes for more on most or all days. (9) But several recent studies have suggested that HIIT may be an even better option. One study showed that while both continuous exercise and HIIT helped with blood pressure control, only HIIT helped reduce arterial stiffness—a predictor of cardiovascular disease in people with high blood pressure. (10)

Brain function

Do you get that feeling of mental clarity after a good workout? It’s not in your imagination. The brain health and mental health benefits of exercise are well documented.

Research also shows that HIIT, specifically, can help improve cognitive function, including short-term memory, verbal memory, attention, and processing speed. It also increases the amount of oxygen the brain gets from the blood. (11)


Exercise is an essential part of diabetes management, and research shows that HIIT may be a wise exercise of choice for diabetes 2 sufferers. Studies have shown that HIIT improves endothelial function, insulin sensitivity, glucose control, and other health effects of diabetes better than continuous exercise. (12)

High-intensity interval training exercises

The great thing about high-intensity interval training workouts is that they can be designed around just about any exercise that you’re able to do at full intensity. You incorporate it into your runs—alternating going all out for a period and then pulling back to a more comfortable pace until you’ve recovered.

For a basic, beginner’s sprint interval, here’s Kelly’s recommendation:

  • Warm up with a 3-minute jog
  • Sprint as fast as you can for 15 seconds
  • Jog for 45 seconds
  • Repeat 10 times
  • End with a 3-minute walk to cool down

Expert insight

“As you get more conditioned, you can sprint faster or decrease your recovery time,” Kelly says. She also points out that this sprint interval can be done on a bike, elliptical, or other cardio equipment. Or if weight training is more your speed, you could do intense bursts of kettlebell swings with periods of rest in between.

man in gym lifting weights

If weight training is more your speed, you could do intense bursts of kettlebell swings with periods of rest in between.

“And because it’s so adaptable, just about everyone can do HIIT,” Kelly says. “It’s all about exerting your body to the best of its ability for a highly intense, short time. Anyone can do it, within their own parameters,” she explains. “If you’re doing a running sprint interval, for instance, you can change it to a jog and then a walk if you’re not able to sprint and then jog. Or if you’re not able to jog, you could do a power walk and then a casual walk. It’s flexible.”

The 4-minute total-body HIIT workout

For a workout anyone can fit into their busy schedule, Kelly designed a high-intensity interval training total-body workout that takes only 4 minutes to complete. This workout is Tabata-style HIIT, which means it alternates 20 seconds of intense work with 10 seconds of rest.

It might be hard to believe that you can get a good workout in 4 minutes, but after giving this workout a try—and feeling the burn—you’ll see just how much you can accomplish in less time than it takes you to make a cup of tea.

  • Burpees for 20 seconds, followed by 10 seconds rest
  • Push-ups for 20 seconds, followed by 10 seconds rest
  • Mountain climbers for 20 seconds, followed by 10 seconds rest
  • Superman for 20 seconds, followed by 10 seconds rest
  • Squats for 20 seconds, followed by 10 seconds rest
  • Tricep dips for 20 seconds, followed by 10 seconds rest
  • Alternating lunges for 20 seconds, followed by 10 seconds rest
  • Plank for 20 seconds, followed by 10 seconds rest

You can use this as a quick standalone workout on days when you don’t have much time, or you can use it as a finisher after your cardio workout—the “peanut butter to your rice cake,” Kelly jokes.

The bottom line

If you’d like to add high-intensity interval training to your fitness routine, first check with your healthcare provider to make sure it’s right for you. Then follow these tips from Kelly for using HIIT safely:

  • Warm up properly
  • Listen to your body
  • Don’t overdo it—as with any exercise, overtraining can lead to injuries

HIIT can be a great exercise choice for people who are short on time or for those who want to supplement their other workouts for a well-balanced fitness program. With not much time commitment, but by giving it your all, you can reap the rewards of this popular and proven fitness approach.

Fullscript simplifies supplement dispensing

Create your dispensary today I'm a patient