We all get older but we don’t all age the way. What if I told you that there is one exercise that will make you feel younger. When you exercise or workout, if you focus on this one thing, it will actually start to reverse the aging process and make a difference.

My joints creak. Both of my shoulders make wonderful little popping noises. I do this groaning thing when try to roll out of bed that I never thought I’d make. (In fact, most of the time I don’t even notice I’m doing it.) If I lie on the floor for a while, getting back up is no longer automatic; it’s a process. Things are happening to my body, both outside and inside.

Fortunately, some of what’s happening on the inside can be mitigated or even reversed–even though, as with most worthwhile results, doing so isn’t easy. (Seriously: Is anything worthwhile ever easy to accomplish?)

Researchers conducted an experiment on men and women divided into two groups: Half were below 30 years old, the other half over 64 years old. (The study is titled “Enhanced Protein Translation Underlies Improved Metabolic and Physical Adaptations to Different Exercise Training Modes in Young and Old Humans,” proving yet again that research paper titling is where fun goes to die.)

Everyone involved in the study was healthy but basically sedentary. Participants were then given different exercise regimens to follow for 12 weeks.

The Way to Exercise That Will Make You Feel Younger

One group did not exercise. Another group alternated riding stationary bikes for 30 minutes at a moderate pace on some days, lifting light weights on others. The third group lifted heavy, and the fourth group did strenuous interval training on a stationary bike: They pedaled hard for four minutes, rested for three minutes, then repeated the cycle for a total of four intervals.

What happened? The control group, as control groups are wont to do, did not improve. (Proving that you should never sign up to be in the control group.) Everyone else made improvements in overall fitness.

That’s no surprise: Good things happen when we exercise. The participants who lifted weights showed an increase in strength and muscle mass. (People who lifted heavy showed a greater increase than those who lifted light.) The participants who rode stationary bikes showed an improvement in cardiovascular fitness. (Those who did intervals showed a much greater increase in endurance, for good reason.)

You knew all that, but here’s what you might not know. As we age, our muscle cells deteriorate. They don’t regenerate as easily as when we’re young, plus we lose mitochondria, which is where our energy comes from. To make it worse, the mitochondria that do remain get weaker.

Or, as the lead researcher said, “It seems as if the decline in the cellular health of muscles associated with aging was ‘corrected’ with exercise, especially if it was intense. In fact, older people’s cells responded more robustly to intense exercise than the cells of the young.”

And keep in mind that interval training doesn’t have to involve stopwatches and rigid formulas. If you’re riding a bike outside, choose a hilly route and work hard on the climbs. If you’re jogging, mix in a series of 30- or 40-second intervals at a three-quarter sprint pace. Count the elapsed time in your head. (If nothing else, counting to yourself may help distract you from the effort.) If you’re at the gym, try a HIIT workout.

The goal is to go well beyond what feels comfortable. Your muscles need to burn. Your lungs need to burn. If it’s not hard– really hard–then you’re not doing intervals.

Via inc.com