Story highlights Candidates' health has emerged as an issue

One third party candidate has said he runs very fast

Washington (CNN) Donald Trump said he is not one to exercise, and Hillary Clinton drew a lot of attention after faltering in public and taking a few days of rest over pneumonia.

Voters truly concerned about fitness could take a look at Gary Johnson.

"I don't want this to be an embellishment, but I will be the fittest president of the United States ever," Johnson said Wednesday in Detroit.

Although President Barack Obama is no slouch, and his predecessor, President George W. Bush, was a regular exerciser, Johnson has a decent case to make.

The Libertarian candidate for president and former governor of New Mexico is an avowed athlete and outdoor adventurer. He said he has climbed the tallest peak on every continent, including Mount Everest.

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