If you're trying to preserve your youth, a HIIT class might work better than anything sitting in your medicine cabinet, according to new research published today in Cell Metabolism.
For the study, Mayo Clinic researchers examined the effects of three different exercise programs—high-intensity intervals on a bike, weight lifting, or a combo of both—on 72 men and women. Half of the participants were 18 to 30 years old and the rest were between the ages of 65 and 80.
After 12 weeks of regular sweat sessions, the researchers examined muscle biopsies taken from the exercisers' thighs. They also evaluated their levels of lean muscle mass and insulin sensitivity, both of which tend to nosedive as we age.
The researchers found that, while all three of the exercise programs enhanced insulin sensitivity—a reflection of a person's diabetes risk—and strength training was the best at building lean muscle mass, only high-intensity interval training (HIIT) and combined training (HIIT plus strength training) improved their age-related decline in muscle mitochondrial capacity.
Mitochondria are microscopic power plants that use oxygen to produce energy. When contained in your body's muscle cells, they are referred to as muscle mitochondria. As we age, our mitochondria's capacity to crank out energy decreases, explains Sreekumaran Nair, a professor of medicine and researcher at the Mayo Clinic and the study's lead author. Interval training increased the younger volunteers' mitochondrial capacity by 49 percent, while the older volunteers enjoyed a 69 percent boost.
Previous studies—many of which Nair's team did—show that a decline in mitochondrial capacity is a key factor in the development of symptoms that we commonly ascribe to aging, like wrinkles and declining health. For instance, their previous research, published in The American Journal of Clinical Nutrition shows that mitochondrial capacity and insulin resistance, the hallmark of Type 2 diabetes, are intricately linked.
However, this study is the first to show that exercise, especially HIIT exercise, actually causes an increase in the body's creation of mitochondria, effectively putting the breaks on aging at the cellular level. And if this happens in muscle cells, it likely happens in heart and brain cells too, Nair says. The finding is integral to understanding exactly how exercise benefits our bodies and, ultimately, how to take advantage of it for better health.
"There is no substitute for slowing aging and increasing life span," Nair says. "There is no pill or form of medicine that can do this." Of course, he and fellow researchers hope that the finding can one day be used to develop a sort of "exercise pill" for older adults who lack mobility and are unable to exercise.
If you want to turn back the clock, HIIT protocols of aerobic exercise like running, biking, and swimming are the single best form of exercise you can do. That said, if you can perform some strength training on the side, even better, Nair says. After all, age-related decline in muscle mass starts as early as age 30 or 40, and if you keep up your levels of muscle mass up as you age, you can go harder, longer, and get more out of those workouts.
To reap the benefits, Nair recommends three to four days of high-intensity interval workouts along with a couple of strength sessions per week.