By Rick Ansorge   |   Thursday, 13 Apr 2017 11:20 AM

The health benefits of exercise are well-established for people of all ages. But until now, little has been known about which type of exercise best counters the aging process in senior citizens.

The answer may be high-intensity interval training, suggests a new study published in Cell Metabolism by researchers from the Mayo Clinic.

High-intensity interval training (HIIT) alternates short bursts of intense aerobic activity such as biking or walking with short periods of easing up on the same activity.

This type of exercise, which originated in Sweden, is promoted as an efficient training method that avoids the risk of injuries associated with non-stop, repetitive activity.

Compared to other types of exercise, it appears to be dramatically more effective at boosting the activity of aging cells and even reversing age-related cellular damage.

The Mayo Clinic researchers recruited 72 healthy but sedentary men and women from two age groups: “young” subjects ages 18-30 and “older” subjects ages 65-80.

The researchers conducted baseline measurements of aerobic fitness, lean muscle mass, blood-sugar levels, and insulin sensitivity. After taking biopsies from the subjects’ thighs, they also assessed genetic activity in muscle cells and the health of the energy-producing mitochondria within those cells.

As we age, mitochondrial capacity gradually deteriorates. As a result, cells become damaged and weak.

The researchers randomly assigned subjects to one of three groups:

HIIT on stationary bicycles. Three days per week, they pedaled hard for four minutes, eased up for three minutes, then repeated the sequence three more times. On other days, they did a moderate treadmill routine,

Moderate-intensity training. Three days per week, they pedaled on stationary bikes for 30 minutes. On other days, they lifted light weights.

Vigorous weight training. Participants engaged in weight lifting several times per week.

No exercise. A fourth group did not engage in organized physical activity.

After 12 weeks, the researchers found that all three exercise groups experienced significant gains in fitness and blood-sugar regulation compared to non-exercisers.

As expected, they found that the high-intensity interval training group had the biggest improvement in endurance while the weight training group had the biggest improvement in muscle mass and strength.

But they were astonished to find that high-intensity interval training was most strongly associated with age-reversing changes at the genetic and cellular levels.

In the “younger” group assigned to high-intensity interval training, the activity level changed in 274 genes. That compared to activity-level changes in 170 genes in the moderate-intensity training group and 74 genes in the weight training group.

Genetic changes were even more dramatic in the “older” group assigned to high-intensity interval training. They saw activity-level changes in nearly 400 genes. That compared to activity-level changes in only 33 genes in the weight training group and only 19 genes in the moderate-intensity training group.

High-intensity interval training had a similar effect on mitochondrial capacity: a 49 percent increase in the “younger” group and a whopping 69 percent increase in the “older” group.

This type of exercise also led to improved insulin sensitivity, which is associated with a reduced risk of diabetes.

The researchers cautioned that their primary goal was to show how exercise works at a molecular level, not to provide prescriptive exercise for seniors or anyone else. They hope to learn more about how exercise benefits different tissues in the body.

For the time being, they say that vigorous exercise remains the most effective way to bolster health.

“There are substantial basic science data to support the idea that exercise is critically important to prevent or delay aging. There’s no substitute for that,” senior author Dr. Sreekumaran Nair said in a statement.

Most experts agree that many older adults can participate in an age-appropriate high-intensity interval training program that takes into account their physical limitations.

Older adults are more likely to have an underlying health issue such as osteoporosis, arthritis, diabetes, hypertension or a history heart disease, heart attack, or stroke.

So it’s essential for them to consult with their primary care provider and take a cardio-stress test before beginning a new exercise program, especially one that involves vigorous activity.