In her 30 years of running, Mary Croft has participated in marathons on five continents, including Antarctica.

She has run a marathon in all 50 states and even organized a 26.2-mile race inside a prison.

Sunday, at the Tucson Marathon, Croft will do something she's never done before - run a marathon on her birthday.

"And it's my Medicare birthday," she said.

Croft will turn 65 Sunday, then line up to run her 167th career marathon.

It's the perfect way to spend her birthday, she figures. She first started running 30 years ago, swept up in the wellness movement as a mother in Minneapolis.

Croft grew up as a tomboy in Papua New Guinea, where her father was a missionary, and at a boarding school in Australia. She didn't live permanently in the United States until 19, when she enrolled at Augsburg College in Minneapolis.

"Culture shock," she said.

She married her husband Dave, had a son, Matthew, and worked as a nurse before running her first marathon at 35.

Croft joined a running club in Minnesota and continued her sport when she became a Tucson resident 12 years ago. She still spends four or five warm months a year in Minnesota.

"I left just in time," she said, "because snowshoeing is really hard."

She joined groups devoted to running - one took a cruise to Antarctica, where they ran on a glacier.

She has run in 50 states, in South Africa, Spain and Russia. In October, she ran the original marathon in Athens, Greece.

"My number is just a drop in the bucket compared to some others," she said.

Her involvement in the Tucson Marathon goes beyond simple participation.

Croft coordinates the 500 or so volunteers at water stations and the finish area.

She e-mails about 15 aid station captains months in advance to make sure they help recruit volunteers.

"She's the most giving person alive that I know of," race director Pam Reed said. "Working with volunteers and working with me - I can be very intense - and she's really a laid-back, great person."

Reed said the marathon will feature between 3,200 and 3,300 participants, up about 200 from last year.

A little more than half the participants will run in the half-marathon. Fifty relay teams of four runners will also compete.

This race will use the route from two years ago, with runners turning around near Biosphere 2 in Oracle.

The change should make the downhill run faster, which is Reed's goal.

Sunday, Croft will be the one smiling, enjoying her birthday, regardless of how fast she runs.

"She's the most energetic person, for being almost 65," Reed said.

"She just goes, goes, goes."

IF YOU GO

• When: Sunday. Half-marathon at 7 a.m.; marathon and marathon relay at 7:30 a.m.

• Finish line: Coronado Middle School, 3401 E. Wilds Road

• Spectator parking: Available at Bashas' Supermarket at 15310 N. Oracle Road