WHAT
High-intensity interval training (HIIT) alternates between brief, strenuous exercise and active rest. You might sprint for 60 seconds, walk for 30, do push-ups for 60, walk for 30, and so on.

HIIT intensely stresses your muscles, then it lets them recover during active rest. Stringing exercises together and maintaining active rest keeps your heart and breathing rates up, so you also get the benefits of aerobic exercise.

Typically, a HIIT workout will range from 10 to 30 minutes in duration.

WHY
Despite how short the workout is, it can produce health benefits similar to twice as much moderate-intensity exercise. Here are some:

• Researchers found that HIIT burned 25–30% more calories than the other forms of exercise (a HIIT repetition consisted of 20 seconds of maximal effort, followed by 40 seconds of rest).
• Several studies have demonstrated HIIT’s impressive ability to increase your metabolic rate for hours after exercise.
• HIIT has also been found to shift the body’s metabolism toward using fat for energy rather than carbs.
• Studies have shown that HIIT can help you lose fat.
• HIIT could help increase muscle mass in certain individuals (increases in muscle mass are more likely to occur in individuals who were less active to begin with and primarily in the muscles being used the most, often the trunk and legs)
• Can improve oxygen consumption.
• A large amount of research indicates that it can reduce heart rate and blood pressure in overweight and obese individuals. 
• Blood sugar can be reduced by HIIT programs lasting less than 12 weeks.

HOW
The actual activity being performed varies but can include sprinting, biking, jump rope or other bodyweight exercises.

Here's one simple setup to get you started. You can check out our Exercise section for more HIIT exercises.

Do each exercise for 60 seconds, and in between do active rest (walk in place) for 30 seconds.

• Jog in place
• Walk in place
• Bodyweight squats
• Walk in place
• Push-ups
• Walk in place
• High jumps
• Walk in place
• Sit-ups
• Walk in place
• Burpees
• Walk in place

If once through isn’t enough, repeat the workout until you’re spent.

You can also try a Tabata-style workout. Tabata workouts (named after their creator, Dr. Izumi Tabata, who used them in his research to great effect) follow a basic structure:

Choose an exercise and do 8 rounds of going all-out for 20 seconds and resting for 10. For example:

• Burpees (20 seconds)
• Rest (10 seconds)
• Repeat 7 more times

It's useful to find a Tabata / HIIT timer when doing these exercises. Check out your App or Play store.