How Long Does It Take for HIIT Results? When You'll See Physical Changes

If you're short on time but still want a good burn from your exercise routine, high intensity interval training (HIIT) may be the best option for getting the most from your workouts.

HIIT is a popular form of exercise due to its efficiency in helping people achieve their fitness goals, Roger Franco, an assistant fitness manager at Crunch Fitness in Fort Greene in New York City, told Newsweek. It entails performing an exercise in a short interval of high intensity, followed by a short interval of rest or active recovery.

"As opposed to moderate-intensity or long-duration exercise, HIIT dramatically improves various health-related factors such as muscular power, fat and weight loss and other health-related benefits such as preventing cardiovascular or metabolic diseases," he said.

How Long Should HIIT Workouts Be?

HIIT workouts should range between 30 and 50 minutes, Steve Stonehouse, a National Academy of Sports Medicine-Certified Personal Trainer (NASM-CPT) and director of education for STRIDE Fitness, told Newsweek.

"Length ultimately depends on how intense your intervals are, but usually a half hour will feel sufficient," he said.

Franco said a typical HIIT workout involves alternating multiple rounds of 30 seconds of sprinting with 30 seconds of walking or doing a circuit of bodyweight exercises. Each exercise is performed for 30 seconds followed by 10 seconds of rest. Most HIIT workouts are commonly between 10 minutes to over 30 minutes, he said.

Women doing a high jump move.
Women doing a high jump move during a HIIT training session. iStock/Getty Images Plus

Dr. Yuri Feito, a certified clinical exercise physiologist and fellow with the American College of Sports Medicine (ASCM), told Newsweek that the length of your HIIT workout also depends on an individual's training goals and fitness level.

For beginners, it's advisable to follow a program that includes the same "work to rest time intervals," such as the 30 seconds of work and 30 seconds of rest routine.

For more advanced individuals, "greater benefits occur when the rest periods are a fraction of the work interval," the exercise physiologist said, such as the 30 seconds of work and 15 seconds of rest combination.

It's important to keep in mind that "high intensity" can be different for everyone, Feito noted.

Most people tend to think that HIIT workouts "should always include work intervals near maximum," but this is not the case, he said.

"There is some evidence that suggests that even a single minute of high intensity activity provides improvements in health markers," according to the ACSM fellow.

Men doing squat exercises outdoors.
A group of men doing squat exercises outdoors. iStock/Getty Images Plus

How Often Should You Do HIIT Workouts?

Feito said there is no formal recommendation indicating HIIT workouts should be limited to a certain number of days a week. For most people, two to three times per week, with a rest day in between, should be appropriate, but the frequency also depends on the person.

For beginners, it would be prudent to start with a single day, see how they feel the next day and progress from there based on their abilities, Feito said.

Franco said HIIT programs are usually scheduled three to six times per week. While duration and frequency are relevant factors in creating successful HIIT programs, "exercising at 80 percent to 95 percent of heart rate capacity is crucial to guarantee desired results," he said.

HIIT workouts are more exhaustive than other workouts due to their high intensity and minimal rest. But one of its key features is being able to modify the intensity according to the individual's fitness level and goals, he added.

A woman doing rope lifting exercises indoors.
A woman doing rope lifting exercises indoors. Typical HIIT training sessions usual entail 30 seconds of intense exercise following by 30 seconds of rest. iStock/Getty Images Plus

Stonehouse said: "You can do HIIT workouts a few times a week, but I wouldn't recommend every single day because they are high-impact workouts. You will want to take at least a day off between HIIT workouts to give your muscles and joints time to recover."

He suggested alternating HIIT workouts with other types of exercise, such as yoga, Pilates, cycling or rowing to maximize your week and prevent burnout.

Feito advised that anyone interested in engaging in this type of training or any vigorous exercise should consult with a medical professional before starting the program.

Franco agreed, noting that "a skilled valuation of a client's mobility level, endurance level, and fitness goal is fundamental to designing a safe and effective program."

An experienced trainer can help you assess and build the most appropriate HIIT program for you, determining the duration, frequency and type of exercise to be used in a circuit, he said.

A man running outdoors.
A man running outdoors. A typical HIIT workout involves alternating multiple rounds of 30 seconds of sprinting with 30 seconds of walking or doing a circuit of bodyweight exercises. iStock/Getty Images Plus

How Long Does It Take to See HIIT Results?

Feito explained: "This is a difficult question to answer as there are many variables that will impact the results of any training program."

Factors including the number of sessions, additional exercise routines, changes in eating habits, among others, will impact the time frame for when you'll see results. These variables should be individualized for anyone engaging in HIIT or any other type of exercise program, he said.

A woman doing the mountain climber exercise.
A woman doing the mountain climber exercise move on a mat during a HIIT training session. iStock/Getty Images Plus

Stonehouse agreed, noting the time it takes to see results will vary based on how often you are working out and other factors such as diet and sleep.

"If you are on a consistent schedule doing a few HIIT workouts a week, you will likely start to see some results within a few weeks such as improved endurance, lean muscle, VO2 max, and possibly even weight loss," he said.

Feito said most inactive adults who start a high intensity program will probably start seeing results within six to eight weeks. Most changes occur first within the body without significant "visual" appeal.

"Visual changes are often dependent on nutritional changes that accompany the physical work. For individuals who are currently active in more moderate intensity work, this timeline may be different," the exercise physiologist said.

A man taking a break during exercise.
A man taking a break during exercise, while hunched over with hands placed on his knees. For those new to HIIT training, it's advisable to follow a program that includes the same work to rest time intervals. iStock/Getty Images Plus