Short and intense, High-Intensity Interval Training (HIIT) is a physical activity that alternates between high and low-intensity exercises to push the body to its limits.
Its popularity stems from the short duration of the sessions—averaging less than 45 minutes, and sometimes as short as 20—and the multiple benefits the body experiences afterward, including improved cardiovascular efficiency, increased muscle mass, and fat burning.
“It’s an anaerobic exercise whose impact is so intense that it can’t be sustained for a long time,” explains HIIT trainer Virginia Zehnder. She adds that it’s recommended to practice it two, three, or at most, four times a week, allowing the body to recover from the exertion on other days.
“It’s absolutely effective. It not only improves health-related aspects but also produces visible physical results in a short time,” she states. Some of the most common benefits include fat loss, improved body composition, and increased muscle tone.
During a single session, the types of exercises vary, from stationary bikes to kettlebells or treadmills, among other equipment. The key lies in the variety and the rest periods between exercises. However, Zehnder advises that if you’re a beginner, it’s important to start slowly with short workouts, which can be intensified as the body adjusts to the effort.
According to Zehnder, a typical HIIT workout might involve performing sprints for 60 seconds with brief 15-second intervals for rest or recovery.
One of the Most Effective for Burning Fat
A study from the University of Victoria in Australia concluded that HIIT is more effective at increasing fat burning than aerobic exercise. Researchers evaluated a total of 511 people who participated in different control groups: supervised HIIT training, moderate-intensity aerobic exercise, and a group that did no exercise.
What were the results? After 12 weeks of continuous HIIT, they found that the participants’ bodies had transformed into “fat-burning machines.” Experts emphasized that those who practiced high-intensity interval training not only burned more fat during training sessions but also during other types of physical activity, such as brisk walking, swimming, and playing sports. This finding highlights the potential for HIIT to have lasting metabolic effects.
The research also details that fat metabolism improved after just four weeks of HIIT and continued to improve over time. Experts emphasized that without a commitment to daily HIIT training, the improvements in metabolic health would not be so noticeable.
Professor Zeljko Pedisic, who led the study, emphasized that for high-intensity interval training (HIIT) to be effective, the heart rate needs to be above 80% of a person’s maximum capacity. He added that HIIT is ideal for those who want to target fat loss in specific areas of the body.
Regarding its benefits, HIIT is a more demanding exercise for physical endurance. Further evidence comes from another study published in the Journal of Physics, which confirmed how resistance, speed, agility, and an athlete’s power improved through HIIT practice. This is because high-intensity training leads to important physiological adaptations, such as improved cardiovascular efficiency—and therefore better oxygen consumption—and increased tolerance to lactic acid accumulation—a substance produced by muscle tissue and red blood cells that carry oxygen from the lungs to other parts of the body.
It’s worth noting that the World Fitness Trends Survey has repeatedly ranked HIIT among the most popular exercises in the world.
“It’s trendy, and that’s due to its obvious results: it improves physical fitness and, at the same time, it’s noticeable how the body acquires good muscle tone and loses fat,” concludes Zehnder.
