People today want it all. Faster cars with lower emissions. Money that makes more money. Food that’s healthy and delicious.
But rarely does an opportunity occur to have your cake and eat it too.
So, when HIIT workouts first came into popularity, claiming that you could reap the benefits of an hour-long workout in a matter of 15-minutes, it quickly became one of the more popular ways to exercise. Not only was it time-efficient, but it also had a catchy acronym.
But is HIIT all it’s cracked up to be?
Today, with nearly a decade of research covering HIIT workouts, we’re much more equipped to answer that question. So, without further ado, let’s dive a little deeper into the data-backed details of HIIT workouts.
What is HIIT?
HIIT — short for high-intensity interval training — is a type of exercise program that alternates between bouts of short, high-intensity training (about 70 to 90% of your maximum heart rate) and brief low-intensity recovery periods (about 60 to 65% of your maximum heart rate).
What Are the Health Benefits of HIIT?
Increase Post-Workout Metabolism
The afterburn effect, also known as EPOC (excess post-exercise oxygen consumption), is a phenomenon where your body continues to burn calories long after you finish a workout. HIIT triggers the afterburn effect, helping you burn more calories without lifting another finger. What’s more, studies suggest HIIT may boost your post-workout metabolism more than jogging or weightlifting.
Improve Oxygen Consumption
HIIT can also improve your body’s ability to utilize oxygen, also known as your VO2 Max. It also has shown to be equally effective compared to traditional steady-state running or cycling. One study showed a 25% increase in VO2 Max among pre-hypertensive participants who performed HIIT on a stationary bike three days a week for eight weeks. 
Increase Muscle Size & Definition
HIIT activates type II muscle fibers, which rely on glycogen for intense exercise. Performing HIIT consistently tells your body that more glycogen is needed to meet the increased demands. As a result, the body adapts by storing more glycogen in your muscles, which causes them to increase in size. 
Enjoy Your Workouts More
Consistency is key when it comes to any workout program. And, the more you enjoy your workouts, the more likely you are to stick with them. According to a study that compared traditional, steady-state exercise routines to HIIT, people who performed HIIT for five weeks reported a higher level of exercise enjoyment than their counterparts. 
Save Time & Torch More Calories
HIIT workouts take much less time than most other forms of exercise because you’re essentially expending the same amount of effort in a shorter amount of time. In addition to saving time, research also suggests that HIIT workouts can burn 25 to 30% more calories than other training methods. 
How Long Should HIIT Workouts Last?
HIIT workouts are flexible, and the total workout time can vary depending on your comfort and fitness level. A typical HIIT workout can vary in duration, ranging from 5 to 30 minutes.
Where Can I Perform HIIT Workouts?
From the gym to the tracks, HIIT workout can be performed almost anywhere, so long as you’re able to easily alternate the intensity of your workouts. HIIT workouts can be performed on a treadmill at the gym or using a set of kettlebells at your local park.
How Long Are HIIT Intervals?
HITT interval cadences — the ratio of time spent training at different intensities — are highly customizable. There isn’t a one-size-fits-all approach. But your end goal should be to push yourself to the upper limits of physical exhaustion during the high-intensity bouts.
That said, there are several tried-and-true HIIT cadences, including:
- 30-30 Intervals: 30 seconds of high-intensity bouts followed by 30 seconds of low-intensity intervals performed for a total of 5 to 10 minutes, depending on your fitness level.
- 20-10 Intervals: 20 seconds of high-intensity bouts followed by 10 seconds of recovery, repeated eight times for a total of 2 to 4 minutes, depending on your fitness level.
- 30-20-10 Intervals: 30 seconds of low-intensity bouts, 20-seconds of moderate-intensity bouts and 10 seconds of high-intensity bouts.
Is HIIT Safe?
Generally speaking, HIIT is safe for healthy, fit individuals capable of performing intense physical activity.
However, as with most health and fitness topics, moderation is key. Daily high-intensity exercise can lead to several adverse side effects, including a decline in mitochondrial function and blood sugar dysfunction.
People who live a generally sedentary lifestyle or have a family history of cigarette smoking, abnormal cholesterol levels, hypertension, obesity or diabetes should consult a physician before trying HITT. It’s also recommended that people new to or returning to a regular exercise routine should perform traditional aerobic exercise 3 to 5 times per week for one month before trying HIIT.