I recently wrote about a study showing that one minute of intense interval training, tucked into a workout that was, in total, 10 minutes long, produced comparable health and fitness benefits to 45 minutes of more moderate, uninterrupted endurance training.
Readers posted almost 400 comments to the article and flooded the Internet and my inbox with questions and sentiments about extremely short workouts. Given the extent of the response and the astuteness of the questions, I thought I would address some of the issues that arose over and over.
Q. Are high-intensity interval workouts actually better for you than longer, endurance-style workouts — or just shorter?
A. Better is such a subjective word. At the moment, the two types of workouts appear to be largely equivalent to each other in terms of a wide variety of health and fitness benefits.
In the study that I wrote about, “1 Minute of All-Out Exercise May Equal 45 Minutes of Moderate Exertion,” for instance, three months of high-intensity interval training practiced three times per week led to approximately the same improvements in aerobic endurance, insulin resistance and muscular health as far longer sessions of moderate pedaling on a stationary bicycle.
One type of workout was not more beneficial than the other, in other words, but one required much, much less time.
Other studies have generally produced similar results, although, to be honest, the science related to interval training for health purposes and not simply for athletic performance remains scant. An interesting new review of past research to be published in June did conclude that, for overweight and obese children, short sessions of intense intervals may lead to greater improvements in endurance and blood pressure than longer bouts of moderate exercise, although the authors did not discuss how best to get children to complete frequent interval sessions.
The upshot of the available science is that if you currently have the time and inclination to complete long-ish, moderate workouts — if you enjoy running, cycling, swimming, walking or rowing for 30 minutes or more, for instance — by all means, continue.
If, on the other hand, you frequently skip workouts because you feel that you do not have enough time to exercise, then very brief, high-intensity intervals may be ideal for you. They can robustly improve health and fitness without overcrowding schedules.
What about combining brief high-intensity workouts with longer, endurance workouts?
Alternating high-intensity workouts with endurance-style workouts may yield the greatest health and fitness gains of all.
In a 2014 study, a group of sedentary adults began either a standard endurance-training program, in which they pedaled a bicycle moderately for 30 minutes five times a week, or swapped one of those bike rides for an interval session. All of the participants wound up significantly more aerobically fit after 12 weeks.
But the men and women who had completed one interval session per week had developed slightly more overall endurance than the other volunteers. As a result, they had lowered their risk for premature death by about an additional 18 percent, the study’s authors conclude.
Do I have to use a stationary bicycle for interval training?
Most recent studies of high-intensity intervals have involved computerized stationary bicycles because scientists can easily monitor the riders’ pace and intensity. But there is nothing magical about the equipment. The key to high-intensity interval training is the intensity, which most of us can gauge either with a heart rate monitor or our own honest judgment.
For moderate exercise, your heart rate typically should be between 70 and 85 percent of your maximum. (I recently wrote about how to determine your individual maximum heart rate.) This intensity would feel like about an 8 on an arduousness scale of 1 to 10.
During an intense interval, however, your heart rate should rise to 90 percent of your maximum heart rate, or above. Think of this as feeling like about a 9.5 on the 10-point scale. You maintain that intensity for only 10 or 20 seconds at a time, however, followed by several minutes of very easy exercise before repeating the intense work.
Almost any type of exercise can be used for interval training, including running up the stairs in your office’s stairwell during your lunch hour, said Martin Gibala, a professor of kinesiology at McMaster University in Hamilton, Ontario, and an expert on intervals. (His book about the science and practical implications of high-intensity interval training will be published in early 2017.)
Will high-intensity intervals help me to lose weight?
Few studies have yet looked at the long-term effects on body weight of exercising exclusively with high-intensity intervals, although some experiments do hint that high-intensity interval training can reduce body fat, at least in the short term.
In a 2015 study, for example, overweight, out-of-shape men who began either to jog or otherwise exercise moderately for an hour five days per week for six weeks or to complete intensive interval training for a few minutes per week all dropped body fat and about the same percentages of fat, despite very different amounts of exercise. Likewise, a group of women recovering from breast cancer who were assigned either to moderate exercise or brief interval training for three weeks lost comparable amounts of body fat during the study.
But these were small-scale, brief experiments. Whether interval training helps or hinders long-term weight control is still unknown.