APU Health & Fitness Original

Sprint Interval Training: A New Method for Physical Fitness

By Kristjana Cook, M.S. 
2022 Master’s Degree Graduate, School of Health Sciences, Department of Sports and Health Sciences

and Daniel G. Graetzer, Ph.D.
Faculty Member, School of Health Sciences

Sprint interval training (also known as SIT) may be just the workout solution for the millions of people who complain about never having enough time to exercise, according to fitness research Nicolas Rizzo of RunRepeat. In the early months of the COVID-19 pandemic, The New York Times ran a scintillating article, “The 4-Second Workout.” The article described a promising study from the University of Texas on improvements in fat metabolism in sedentary individuals who incorporated multiple rounds of four-second, all-out sprints into their otherwise sedentary workday.

According to Healthline, the tantalizing idea of “exercise snacks” soon became a new fad for busy individuals looking to get in shape without the lengthy time commitment required for traditional exercise programs. The Washington Post also ran an article outlining the benefits of trading a lengthy moderate workout for a quick, heart-pumping one.

The science is there to back up the effectiveness of sprint interval training. The European Journal of Applied Physiology published a study comparing participants who did all their bouts of exercise in one session versus a group that spread micro-workouts throughout the day. According to the study, the micro-workouts were just as effective for participants.

How Does Sprint Internal Training Work?

sprint interval training 2 Cook Graetzer
With sprint interval training, a runner performs very short bursts of activity to maximum capacity, followed by a rest period.

Sprint interval training involves an exerciser performing very short, high-intensity bursts of physical activity to his or her maximum capacity. That exercise is then followed by adequate amounts of complete rest.

It’s important, however, not to confuse sprint internal training with a more commonly known exercise method called High-Intensity Interval Training (HIIT). This type of training makes up the premise behind workouts like Orange Theory, Les Mills, CrossFit and similar exercise routines popular in gyms throughout the United States.

The Harvard School of Public Health notes that HIIT workouts are highly effective. They typically involve one- to six-minute bouts of exercise at about 80% of maximal effort, followed by a short period of rest. This pattern of exercise is then repeated eight to 12 times.

HIIT sessions can last from 30 minutes to longer than an hour, depending on the level of the workout. While shorter than a traditional moderate aerobic workout, HIIT workouts are incredibly concentrated and require repeated submaximal intervals to reap their maximal potential cardiovascular benefits.

By contrast, sprint interval training sessions are much shorter overall, with intervals lasting four to 10 seconds followed by several minutes of rest between intervals, then repeated four to 10 times. The key is attaining 100% all-out physical effort. If that sounds impossible, remember that it’s a short time to endure.

The rest periods are significantly longer than HIIT as well; with sprint interval training, you need to allow your heart rate to return close to its normal resting rate before beginning another round. That rest period enables the body’s metabolic system to recuperate from the anaerobic response to the sprint.

For most people, this rest and recuperation period will take two to five minutes. So if you find your energy level returns to normal before the two minutes are up, you’ll know that you weren’t exercising hard enough and will need to work out a little harder in the next session.

Interspersing these miniature workouts throughout the day is no less effective that doing them all at once, according to a study published by the American College of Sports Medicine (ACSM).

What Are the Physical Benefits of Sprint Interval Training?

According to research from the Journal of Sports Sciences, the Journal of Physiology, Frontiers in Physiology, and Science Direct, two to three sessions of sprint internal training per week can have multiple physical and mental benefits, including:

  • Improved cardiovascular health
  • Increased endurance
  • Reduced body fat
  • Improved muscle density
  • Improved metabolism
  • Reduced depression and anxiety
  • Improved mood
  • Increased self-confidence
  • Improved feelings of enjoyment and empowerment

Sprint interval training sessions can involve different types of exercise. For instance, an exerciser could perform sprints on a track, use a spinning bike, run up a few flights of stairs, do burpees or do plyometric training in a gym.

For busy adults, this novel way of approaching exercise might be the “fitness hack” of their dreams. With minimal time commitment and equipment, no gym membership, no coach and unlimited flexibility, all you really need to succeed is the willpower to find your maximum limits.

Who Can Benefit from Sprint Internal Training?

Everyone can benefit from sprint interval training. The advantages and performance benefits of sprint interval training have been studied on:

  • Men and women
  • Children, adolescents, adults and the elderly
  • Competitive athletes
  • Sedentary, untrained individuals
  • Overweight and obese patients
  • People diagnosed with clinical depression and anxiety

According to the Royal Society of Canada’s Academy of Science, researchers directly compared moderate intensity aerobic training to much shorter sprint interval training workouts during a study on the effects of sprint interval training on healthy but untrained overweight and obese women. Both groups saw the same improvements in increased VO2Max (the maximal amount of oxygen your body can utilize during peak intensity exercise), muscle gain and overall body composition.

But the women in the sprint interval training group reported a higher level of enjoyment with the workouts and better adherence to regular exercise. They also completed their workouts in about a quarter of the time.

In another study on healthy, untrained women with a normal body mass index (BMI) published by Frontiers in Physiology, researchers compared workouts using either high-intensity interval training or sprint interval training in women. The women performing sprint interval training sessions lost more weight overall than the high-intensity interval training group and significantly improved their BMI. Their workouts lasted about half the time of the high-intensity interval training workouts.

RELATED: Why Cooldowns After Exercise Are as Important as Warmups

Is Sprint Interval Training Too Good to Be True?

It is important to look at the disadvantages and contraindications of sprint interval training as well as the benefits. For instance, does sprint interval training increase the risk of injury?

The easy answer is no according to the Mayo Clinic, provided you are healthy enough to exercise. If you have a prior medical history of cardiac problems, diabetes, or injuries involving a joint, tendon, or bone, always check with a doctor before you begin an exercise program to make sure it’s safe for you.

Other big questions people ask in regard to sprint interval training are what is maximum effort and how to achieve it. The American Council on Exercise (ACE) explains how to determine one’s level of effort by using a rate of perceived exertion.

Maximum effort is something you won’t be able to do for very long during a workout. Even elite, highly trained athletes like Usain Bolt are only able to sustain true maximum effort for 10-30 seconds.

Sprint interval training sessions are supposed to be uncomfortably hard but not painful. If your body suddenly hurts or if you feel lightheaded, nauseous, or feel unable to breathe, you should stop exercising immediately. But if you find yourself merely desperate for that 10-second session to end, then you are on the right track.

RELATED: Plyometrics and the Improvement of Athletic Performance

Is Sprint Interval Training the Workout of the Future?

There is great potential that sprint interval training will last far beyond the “get fit quick” idea used for its marketing. For a non-exerciser or someone daunted by the time and financial limitations of joining a gym or an exercise class, sprint interval training workouts can be beneficial. They are accessible, efficient, and flexible, and they are now proven to improve physical and mental health and vitality across one’s entire lifespan.

Also, sprint interval training does not have to be an all-or-nothing scenario. For example, a recreational runner prone to injury could replace a moderate intensity run each week with a heart-searing sprint interval training track workout.  According to Training4Endurance, that strategy would benefit runners by improving body composition, advancing bone and muscular adaptations, and even potentially lowering the risk of injury from overuse. This “less-is-more” approach to training could be implemented to prepare for events ranging from a 5K to a marathon.

Sprint interval training could be particularly useful for overly busy persons, with the physical and mental benefits comparable to moderate-intensity training sessions lasting four times as long. Sprint interval training has already proven to be life-changing for both males and females, adolescents, overweight/obese adults, and seniors.

About the Authors

Kristjana Cook

Kristjana Cook, M.S., earned a B.A. in anthropology from The George Washington University in 1996. In 2022, she earned her master’s in health sciences with a concentration in exercise science and human performance from American Public University, maintaining a 4.0 GPA. Her capstone project, written under the direction of Dr. Graetzer, was “Reframing the Female Athlete Triad and Reconsidering Mindsets and Training Methods for Female Distance Runners Across the Lifespan.” Kristjana is an American Council on Exercise (ACE) Certified Personal Trainer, certified Road Runners Club of America (RRCA) Level 1 Running Coach and has qualified to run the Boston Marathon multiple times.

Daniel Graetzer

Daniel G. Graetzer, Ph.D., received his B.S. from Colorado State University/Fort Collins, a M.A. from the University of North Carolina/Chapel Hill, and a Ph.D. from the University of Utah/Salt Lake City. He has been a faculty member in the School of Health Sciences, Department of Sports and Health Sciences since 2015. As a regular columnist in encyclopedias and popular magazines, Dr. Graetzer greatly enjoys helping bridge communication gaps between recent breakthroughs in practical application of developing scientific theories and societal well-being.

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