IN AN ACTIVE, OUTDOOR TOWN LIKE BOULDER, COLORADO, IT SEEMS AS IF EVERYONE IS IN TRAINING FOR SOMETHING.

WENDY BOOKER IS NO EXCEPTION. SHE'S AN EXPERIENCED MARATHON RUNNER AND MOUNTAIN CLIMBER BUT UNLIKE MOST, SHE'S DOING IT ALL WITH MULTIPLE SCLEROSIS, A CONDITION THAT OFTEN INVOLVES WEAKNESS AND PAIN.

THE FIRST SIGN CAME WHEN A SUDDEN NUMBNESS IN BOOKER'S LEFT LEG SPREAD UP TO HER RIBS.

WENDY: It's very difficult to receive news that you have a chronic illness that you're going to live with the rest of your life.

AFTER INITIALLY EXPERIENCING ANGER AT HER DIAGNOSIS, SHE RESOLVED TO FIGHT BACK.

WENDY: I thought I'm going to pick something totally out of my realm of thinking to see how far I can push back on my disease. So I thought, why not do the Boston Marathon//I'd never run four miles, much less 26. But I thought here's the ultimate way to see if I can do it.

IT TOOK A YEAR OF TRAINING, BUT SHE COMPLETED THE GRUELING RACE.

WENDY: Then my family and friends thought life would go back to the way it was before the marathon. But no.

LOOKING FOR ANOTHER CHALLENGE, BOOKER JOINED A GROUP OF MOUNTAIN CLIMBERS--ALL, LIKE HER, WITH MS. THEIR MISSION: CLIMB MT. DENALI.

WENDY: And I was so arrogant, I thought I've run the Boston marathon how hard can a mountain named Denali be?

SHE SOON LEARNED THAT DENALI IS ANOTHER NAME FOR ALASKA'S MT. MCKINLEY, THE HIGHEST PEAK IN NORTH AMERICA.

WENDY: That took me way back because then I knew I was facing something that I was very ill prepared for.

PREPARING FOR DENALI WOULD BE DAUNTING FOR ANYONE, BUT HAVING MS MEANT BOOKER NEEDED TO WORK EVEN HARDER.

JENNIFER: She has numbness in her left side particularly her left foot. With mountain climbing it's very important that we focus on her balance. So we do a lot of balance training.

WENDY: Getting overheated is a huge issue because it will make my symptoms far more severe and cause a lot of muscle weakness. But that is something too that I have learned to deal with when I climb.

AFTER MORE THAN A YEAR OF RIGOROUS TRAINING THE GROUP SET OUT TO TACKLE THE MOUNTAIN. BAD WEATHER PREVENTED THEM FROM REACHING THE SUMMIT, BUT FOR BOOKER, THE EXPERIENCE WAS PROFOUND.

WENDY: I sat on that mountain and I started to realize what it's like to have MS. McKinley came to represent more than a mountain to me. McKinley came to represent what life with MS is really like. We can't always do what we want, when we want. and conditions often mandate that we dig a little deeper.

UNDAUNTED, BOOKER RESOLVED TO TRY AGAIN--THIS TIME TO REACH NOT JUST THE TOP OF MCKINLEY, BUT ALL SEVEN SUMMITS, THE TALLEST PEAKS ON EACH OF THE SEVEN CONTINENTS. IT'S A MISSION SHE HAS NEARLY COMPLETED.

BECAUSE SYMPTOMS VARY, NOT EVERYONE WITH MS IS CAPABLE OF SUCH FEATS, OF COURSE.

BUT BOOKER SAYS HER EXPERIENCE OFFERS LESSONS FOR EVERYONE, REGARDLESS OF ABILITY LEVEL.

WENDY: This is really what it is. I realized when I'm on those mountains I'm scared, it's difficult I can't breath, I want to go home, this wasn't the life I expected, but this perseverance this idea that anybody with ms or any chronic illness or anybody can do whatever they want. And that's what those mountains have come to represent."