In the 1990s, Irisawi Koichi began using a high-intensity interval training (HIIT) technique with the Japanese Olympic speed skating team. The skaters alternated 20-second rounds of intense exercise with 10-second periods of rest for a total of four minutes. The results were impressive, and another coach on the Olympic team wanted to better understand what was happening.
Izumi Tabata, PhD, and his colleagues at the National Institute of Fitness and Sports in Japan set out to take a closer look.
Dr. Tabata’s team put exercisers on stationary bicycles that measure parameters such as power output and oxygen use. First, they asked the exercisers to pedal at a moderate intensity, measured as 70 percent of maximal oxygen uptake (VO2 max), for one hour per day, five days per week.
VO2 max is a measure of the body’s maximum capacity to transport and use oxygen during exertion. It’s a combination of how much oxygen-rich blood the heart can pump and how efficiently the muscles can extract the oxygen and use it. As exercise intensity increases, oxygen consumption rises—to a point. Once a person reaches VO2 max, oxygen consumption can’t rise any higher, even as intensity increases.
When a person reaches their VO2 max, the body transitions from aerobic (with oxygen) metbolism to anaerobic (no oxygen) metabolism.
The second half of the study analyzed the effects of high-intensity intervals in a subset of exercisers from the first group. The researchers used monitoring equipment to make sure that exercisers reached 170 percent of their VO2 max for 20 seconds before taking 10 seconds of rest. Exercisers completed eight cycles for a total of four minutes, four days each week. On a fifth day, they added one session of steady-state training at 70 percent VO2 max.
Dr. Tabata’s study showed that the four-minute training protocol improved both aerobic and anaerobic fitness at the same time. Furthermore, a single four-minute session burned the same number of calories as a 60-minute jog. Once the study was published, Dr. Tabata’s name became shorthand for the exercise strategy.
A four-minute workout certainly sounds attractive, but the Tabata class at the gym is unlikely to lead to the same results researchers saw in a laboratory setting. The 20-second intervals in the study were done at an intensity that few people can manage to attain, let alone sustain. “If you feel O.K. after the session, you have not done it right,” Dr. Tabata explained.
That’s not to say that interval training outside of the laboratory isn’t beneficial—studies show that it most certainly is—it’s just not the actual Tabata protocol, and it’s not likely to get you fit in just four minutes.
Even if you can’t max out your body’s ability to use oxygen, you can reap rewards from alternating periods of working as hard as you can with periods of rest. The rest periods can give you just enough of a breather to allow you to work at a higher intensity than you would with a steady state of exertion.
Studies suggest that a shorter, more intense workout can be more beneficial than a longer period of steady-state work. Like Tabata, HIIT improves both aerobic and anaerobic fitness. Aerobic (cardiovascular) fitness strengthens the heart and lungs, while anaerobic fitness improves the ability to move in ways that require us to be quick and powerful.
HIIT is safe and adjustable for people of any age. A young, fit person might have to sprint to reach their maximal effort, while an older person or beginner exerciser may reach that same level with a brisk walk. If you have a medical condition, after talking to your physician, try starting with a shorter exercise period and work your way up as your strength builds. If you have hip, back, or knee problems, try water exercise to get the benefits of interval training without taxing your joints.
For a complete workout, start with a 10-minute warm-up, complete four rounds of four-minute HIIT exercises, and cool down for five minutes. You can do this type of routine two to three times per week separated by a non-interval style of exercise on the in-between days.
You can apply HIIT principles to any type of cardiovascular exercise. Here’s an example of how you could use it with walking.
Warm-up by walking at your normal pace (about 3.5 to 4.0 miles per hour) for 10 minutes. Speed up by half a mile per hour for 20 seconds then slow down for 10 seconds. Complete eight rounds. If you’re using a treadmill, try hill repeats. Walk at your normal speed with the incline set to zero to warm-up; then increase the incline to 3 to 5 percent for 20 seconds. Drop back to zero for 10 seconds. Complete eight rounds.
