As the Evans family runs through Minnesota this week, it's team captain Shamus whose spirit will be fueling his father Shaun's legs.

That's the formula they've used in other long-distance runs as Shaun Evans – a 39-year-old ultra-marathon runner from upstate New York – pushes Shamus, an 11-year-old who was born with cerebral palsy and uses a wheelchair.

The Evans family embarked on "Power to Push 2017" over the weekend when they left Moorhead on a monthlong journey that will take them along the length of the Mississippi River to Lake Charles, Louisiana.

Shamus' mother, Nichole, and his younger brother, Simon, are the support team. They ride close by in an RV.

They've crossed the country this way

In 2013 the Evans family, with help from the group Ainsley's Angels of America, was able to get a "running chariot" for Shamus that allows him to accompany his dad on long-distance running events and races.

Their first was an ultra marathon that involved running 45 miles in six hours.

When that went well, they got more ambitious. In 2015 Shaun and Shamus ran all the way from Seattle to New York City, raising money to buy other disabled children the same kind of chariot Shamus has.

On this month's trip, the Evanses are also raising money (you can donate here), and donating chariots to families along the way (see a video of their first donation here).

Power to Push 2017 is stopping in Little Falls on Monday night. The next few stages will have them staying in Monticello, St. Paul, and Lake City, Minnesota, before reaching La Crosse, Wisconsin, Friday. The itinerary is here.

Why do they do this?

The family says they want to spread the gift of mobility and athleticism to children who do not have the use of their legs.

“Shamus loves roller coasters and downhill skiing, but he can’t make his body do that," Shaun told Fan Sided a couple months ago. "He relies on external forces to make that happen for him whether that be a roller coaster or my legs. He loves the sensation, so I have the honor and the privilege to be his legs.”

Shaun told the website triathlons may be the next challenge he'll tackle with Shamus.