In 2002, Ellen Miller became the first (and is still the only) American woman to summit Mt. Everest from both the Tibet and Nepal sides. After two subsequent hip replacements—for most people, such surgeries would have meant retiring the crampons—she went on to become the first American woman, at age 54, to complete the Everest Trilogy (Everest and nearby peaks Lhotse and Nuptse). We caught up with Miller, now a coach at the Vail Vitality Center who specializes in older athletes, to discuss aging actively.

5280 Health: What training wisdom can you impart to us mere mortals?

Ellen Miller: For years we thought harder training was the way to go. Now we know that smart training is better. That includes rest days. If you’re pushing, pushing, pushing every day, you’re not going to achieve the outcome you’re looking for. There are physiological processes that happen on easier days that can’t happen when you’re working harder.

As a coach, how do you tackle an older athlete’s self-doubt?

I have a little saying: “Your cells have ears.” The neural pathways in our brains are little grooves. If you think negatively about your body, your brain goes to that pathway of anger or fear or frustration. If I can convince the athlete to take that negativity away, he or she can create a new neural pathway. That’s one reason I use the outdoors for my sessions. People’s brains light up when they’re outdoors as opposed to in a gym.

Did you have to conquer your own self-doubt after your hip replacements?

Absolutely. My surgeon had me visualizing my body accepting my new titanium hip. He had me visualizing running and skiing. We know from studies that visualization works.

What’s the greatest fitness challenge for older people?

Staying active and getting outdoors. There are little molecules floating around outside called negative ions. When we breathe [them] in, we produce serotonin, one of our feel-good chemicals. An aging person’s world can become very limited if they’re not spending time in nature.

Nature is one thing—but in your own life, you take time outdoors to another level. What are you most proud of?

The Everest expeditions. It’s very thrilling, for just one moment, to stand as the highest person on Earth. Honestly, I’m shocked I’m still the only American woman who has climbed it from both Nepal and Tibet. I feel very honored and incredibly blessed to have that title.