Suffolk resident Lisa Davis accomplished the seemingly impossible this week: she ran seven marathons in seven days on all seven continents.

“That’s just ridiculous,” Davis said Wednesday, speaking by phone from Punta Arenas, South America. “Who does that?”

But Davis and eight others in her group did just that in the last seven days, beginning in Australia last Wednesday. They then ran 26.2 miles each in Singapore, Egypt, the Netherlands, New York, Chile and Antarctica to complete a marathon on every continent.

Davis, a retired Marine major, did it in about seven days and 30 minutes. She is believed to have become the fastest woman to accomplish the feat by about 22 hours, according to the National Black Marathoners Association.

Some of the others in the group completed it in less than seven days, or 168 hours, Davis said, though there were seven dates on the calendar.

“I was so excited to see that finish line (in Antarctica) that I just broke out in a dance,” Davis said. “As soon as I touched my big toe over the finish line, I just did a dance.”

Davis said the experience was rough.

“It was a lot more stressful than what my mind thought it would be,” Davis said. “It takes a toll on you, because your body doesn’t recover.”

The heat index was about 103 degrees Fahrenheit in Singapore. There were several days in a row that the runners didn’t get to sleep in a bed.

“I literally mean run-fly-run-fly,” Davis said. “It was no surprise that I got sick, because you just can’t recover. And the climate change was intense.”

Davis ran the last two races with flu-like symptoms, she said. Unfortunately, they were also the hardest two even without feeling ill.

“It’s a toss-up between Antarctica and Punta Arenas (Chile),” Davis said of her most difficult race.

The marathon in Punta Arenas was blistering cold and run all on concrete, Davis said. To top it off, she was sick and exhausted. She said she ran about four miles and power-walked the rest.

The group then arrived on King George Island, Antarctica, and had to hike three miles to their campsite, with their gear, before they started running the marathon.

She wasn’t expecting Antarctica to be so hilly, she said.

“It’s all rocks of different sizes, from a marble to a watermelon, and that’s what you’re running on,” she said. “The wind and blistering cold are to the point it makes you cry.”

The vagaries of travel alone would have been enough to keep weaker folks from completing the challenge. In two races, the runners completed the race on empty stomachs because they didn’t have time to eat.

“We just got off the plane and started running the race,” Davis said.

They also ate “a lot of unhealthy things,” such as pizza and airplane food, just to make it through, Davis said.

They likely logged at least another marathon — most of it at a full sprint — getting through the airports to their gates.

“You don’t have any idea how many miles we put on our body just sprinting from one gate to another,” she said. “It was running, running and more running. This was a whole running adventure.”

But, now that it’s all said and done, Davis said she would definitely do the challenge again. Besides getting ill, she had no physical after-effects suffered by others in her group, such as blisters or pulled hamstrings.

“I always tell people you don’t know what you’re made of until you do something challenging,” she said. “You learn something about yourself. You come face to face with all your demons. This will show you what you can absorb as far as a challenge or adversity.”