Exercise—When Less Is More

by Carole Jackson, Bottom Line Health

How many times have you said, “I don’t have time to exercise”? I’m sorry to tell you, but after you read this story, that excuse won’t work anymore.

A new study found that just three 30-minute sessions a week of a fancy-sounding type of activity called Modified High-Intensity Interval Training (MHIT) is an effective way to strengthen your cardiovascular system, which can lead to increased fitness, strength and weight loss. (It’s a lot like regular interval training, which you’ve surely heard of, but the intervals are even shorter.)

If it sounds hard, don’t sweat it. Researchers found that even cardiac rehab patients can handle MHIT—and gain from it.


The gist of MHIT is that it requires just three 30-minute sessions a week, ideally spaced a few days apart. So each workout is quick, but you work very hard during those short spans. Beyond a five-minute warm-up and a five-minute cool-down, it always involves some sort of aerobic activity, generally running, cycling or rowing. You alternate going at an easy pace for one minute with going “all-out” the following minute, repeating that two-minute pattern 10 times in a row.

Researchers in Canada were curious to see if a three-month regimen of short bursts of MHIT might help people who were in cardiac rehab (for either heart disease or heart attack) strengthen their cardiovascular systems more than they would by following a longer, standard exercise program done at a more moderate pace.

Here’s how the study worked: Researchers placed 22 male cardiac patients in either an MHIT program or a standard “moderate endurance” program. Both groups focused on stationary cycling, but the MHIT group did three weekly 20-minute sessions that consisted of the intervals described above, while the traditional exercise group did three longer weekly sessions (30 to 50 minutes) at a consistent moderate pace the entire time. Each group did a five-minute warm-up and a five-minute cool-down before and after each exercise session.

The findings: By the end of three months, both groups of exercisers showed virtually equal improvement. Blood flow improved by 41% in the MHIT group and 42% in the endurance group, and oxygen consumption improved 27% in the MHIT group and 19% in the endurance group. But the interesting part is that the MHIT group did it with just 90 total minutes of exercise per week, while it took the moderate exercise group a total of 120 to 180 minutes a week to achieve the same goal.

To discuss the study results, I called the study author, Maureen MacDonald, PhD, associate professor in the kinesiology department at McMaster University in Hamilton, Ontario. She explained that when your heart is forced to work at a higher-intensity level during MHIT, you can reap the same benefits in less time. I was surprised that cardiac rehab patients could handle such intensity, but Dr. MacDonald said that MHIT actually does not put any more stress on the heart than the standard exercise routine, because the “rest” intervals allow the heart to recover, so the heart doesn’t get overworked.


If you’re interested in trying MHIT yourself but you have a serious health condition, Dr. MacDonald advises that you check with your doctor first. (Dr. MacDonald did not include people with chronic heart failure in her study due to the severity of the condition.) Otherwise, why not give MHIT a shot? MHIT needs to be done only three days a week, so you still can do strength training and stretching on other days of the week.

To try MHIT, choose your favorite aerobic exercise—whether it’s jogging, cycling or rowing—and follow these guidelines from Dr. MacDonald…

  • Warm up for five minutes by lightly doing whatever aerobic activity you choose, so your breathing is light.
  • For the one-minute intensity cycles, either increase your speed, increase your incline (such as running uphill) or increase the resistance if you are using gym equipment such as a stationary bicycle or elliptical machine. If you can keep track of your heart rate, either through a monitor that you wear or through a monitor on the machine that you’re using, increase your heart rate to 80% to 90% of your maximum rate. To determine your maximum heart rate, subtract your age from 220. It should be very difficult to carry on a conversation at this pace, and your muscles should feel like they are working very hard.
  • For the one-minute recovery cycles, do not stop the activity, but simply slow your speed or reduce your incline or resistance back to normal. Your heart rate should be about 10% of your maximum (or about your “warm-up” pace). You should be able to carry on a conversation easily at this pace.

After 10 of these two-minute cycles, cool down for about five minutes (or until your heart rate goes below 100 beats per minute) by lightly continuing the aerobic exercise to bring your heart rate down.

Source: Maureen MacDonald, PhD, associate professor, department of kinesiology, McMaster University, Hamilton, Ontario, Canada.