Are you familiar with the saying “Less is more”? In the realm of fitness, high-intensity interval training (HIIT) is a prime example. These workouts, defined by alternating short bursts of vigorous exercise with brief rest periods, pack an impressive number of health benefits into a small time frame — sometimes as little as four minutes!
Because HIIT is more intense than other workout types, it may not be appropriate for everyone. Check with your doctor first if you are new to exercise, are recovering from injury, or have a medical condition like an uncontrolled heart rate (known as arrhythmia), diabetes, or diabetes complications like retinopathy, per the Harvard T.H. Chan School of Public Health.
Read on to learn about seven potential health benefits of HIIT workouts.
1. HIIT Can Improve Your Fitness Level
Like other cardio activities, HIIT can boost overall fitness. However, it offers unique benefits that can’t be matched by steady-state cardio workouts.
Consider the findings of a landmark study published in 1996 that found HIIT workouts improved cardiorespiratory fitness markers like anaerobic capacity and VO2 max. Anaerobic capacity is the maximum amount of energy a person can generate without oxygen to sustain high-intensity exercise, as defined in another review. If you can produce a lot of energy without oxygen, you’ll be able to lift heavier weights, do more repetitions, and go faster during high-intensity efforts. VO2 max, or maximal oxygen consumption, is the maximum amount of oxygen a person can utilize during intense exercise, with higher VO2 max typically being linked to improved performance, per the University of Virginia.
The 1996 study — dubbed the Tabata study after its main author and creator of the HIIT workout being studied — found that performing four HIIT workouts per week for six weeks improved anaerobic capacity and VO2 max in young athletes. Meanwhile, performing five moderate-intensity cardio workouts for six weeks only improved VO2 max, leading the authors to conclude that HIIT challenges both aerobic and anaerobic energy systems (or oxygen and nonoxygen energy systems).
The best part? Each HIIT workout lasted only four minutes, not including a warm-up or cooldown. The workout is now known as the Tabata protocol and involves alternating 20 seconds of near-maximum effort exercise with 10 seconds of rest for eight rounds.
A more recent study found that Tabata workouts meet American College of Sports Medicine (ACSM) guidelines for improving cardiorespiratory endurance, which say you need 30 minutes of moderate-intensity aerobic exercise five days per week or 20 minutes of vigorous-intensity aerobic exercise three days per week. One caveat: The Tabata workouts used in the study lasted 20 minutes instead of the standard four minutes.
2. HIIT May Improve Overall Heart Health
Boosting your fitness level with HIIT not only makes it easier to do daily activities like climbing stairs or carrying a bag of groceries, it also keeps your ticker healthy. “By improving cardiovascular fitness, your heart, lungs, and blood vessels will more efficiently do their jobs, and you’ll reduce your risk of developing heart disease,” says Aimee Nicotera, an ACSM-certified personal trainer on Cape Cod, Massachusetts.
One review of 11 studies even found that HIIT can boost heart function by increasing the blood that the heart can pump to the rest of the body in each heartbeat and making the arteries (blood vessels that transport oxygen-rich blood through your body) more flexible.
“The easier it is to pump blood through your body, the less taxing it is on your heart,” Nicotera says.
3. HIIT May Lower Blood Pressure
Another way HIIT can help your heart: by lowering your blood pressure. According to the Centers for Disease Control and Prevention, having high blood pressure can increase your risk for heart disease, primarily if the high pressure is not controlled (a condition known as hypertension).
Research suggests that HIIT may lower blood pressure in people with and without hypertension. In one study, healthy men age 56 to 67 who performed one HIIT session per week for six weeks saw an average blood pressure reduction of 5.5 mm/Hg.
In another small study, HIIT helped patients with hypertension return their systolic blood pressure (the pressure in the arteries when the heart beats) to a normal range without medication. Patients performed three HIIT sessions per week for a total of 24 sessions.
4. HIIT May Boost Brain Health
When you exercise, your brain produces brain-derived neurotrophic factor (BDNF), a molecule that plays an important role in creating and maintaining brain cells, per research.
But HIIT may have the advantage over other workouts, as BDNF levels increase with exercise intensity, research finds. Because BDNF helps create new brain cells and sustain existing ones, producing more of this molecule may improve cognitive skills like thinking, memory, and multitasking, says Carlsbad, California–based Pete McCall, CSCS, an American Council on Exercise–certified personal trainer, the national director of fitness education for EoS Fitness gyms, and the author of Ageless Intensity: High-Intensity Workouts to Slow the Aging Process.
5. HIIT May Increase Bone Density
Your body is continually removing old bone and replacing it with new bone. This process is called remodeling, and it keeps your bones strong and dense. That is, until about age 40, when less bone is replaced, per the American Academy of Orthopaedic Surgeons. With less new bone available, your bones can become weak, increasing your risk for osteoporosis (a bone disease characterized by low bone density) and fractures (broken bones).
Weight-bearing activities such as HIIT can help slow bone loss. “There is evidence suggesting that HIIT workouts improve bone mineral density, particularly when they include an emphasis on resistance training,” says Rita Roy, MD, CEO of the National Spine Health Foundation in Washington, DC.
One review of six studies in postmenopausal women with osteoporosis found that high-intensity resistance training that included high-impact jumping exercises created significantly greater improvements in lumbar spine bone mineral density than moderate-intensity resistance training that included high-impact exercises. The length of the training programs varied across studies, ranging from 24 weeks to 13 months.
6. HIIT May Improve Insulin Sensitivity
When you exercise, your muscles make use of glucose (sugar) acquired from food without needing insulin, a hormone that helps shuttle glucose into your cells for fuel when your body is at rest.
For people with diabetes, this makes exercise a game changer, says Samuel Werner, DO, a board-certified family medicine physician at Family Osteopathy in West Hartford, Connecticut. As the effects of your workout on glucose transport wear off, it’s replaced by an increase in insulin sensitivity, notes a research paper. Insulin sensitivity refers to your body’s responsiveness to insulin, and it’s key for type 2 diabetes prevention and management.
HIIT may be a time-efficient exercise method for improving insulin sensitivity. One study in adults with obesity found that 12 weeks of HIIT and moderate-intensity aerobic exercise led to similar improvements in insulin sensitivity (up to 20 percent greater) the day after exercise. However, the HIIT sessions had the advantage of being considerably shorter than the moderate-intensity ones (approximately 25 minutes including warm-up, cooldown, and rest periods versus 45 minutes).
7. HIIT May Help With Weight Loss
Research suggests that HIIT can be an effective weight loss tool. In one randomized, controlled trial, 12 weeks of moderate-intensity aerobic exercise and HIIT had comparable weight loss results (an average of 13.2 and 12.5 pounds, respectively) in 32 adults with obesity. However, the HIIT workouts were an average of 10 minutes shorter than the moderate-intensity ones, making HIIT more time efficient.
HIIT may be effective for weight loss because it burns calories during and after the workout. The post-workout calorie burn is a phenomenon known as excess post-exercise oxygen consumption, also commonly called after burn. Your body needs more oxygen and calories to recover from high-intensity exercise than low- or moderate-intensity sessions, leading to more calories burned in the post-workout hours, per the National Academy of Sports Medicine.
For example, research shows that, while nine men burned fewer calories during a 20-minute HIIT session than they did during a 50-minute steady-state cycling workout, they burned the same number of calories for 24 hours after each workout.
Burning calories during and after HIIT may help you reach a calorie deficit for weight loss when paired with healthy food choices.