PORTLAND – Postman Mark McAfee, 47, rode 23 miles to and from work each day, braving wind, rain and killer dump trucks.

Steve Harris, 45, used his shiny Trek 7200 to teach his two stepdaughters, ages 9 and 11, to pedal safely to school.

Kidney-transplant recipient Martha Black, 57, raced her bicycle in Maine’s Senior Olympics and is training for the U.S. Transplant Games to be held in Minneapolis in late July.

Their stories and those of the 47 other Portland-area residents who received new bicycles for free last summer were detailed in the cover story of the January-February issue of Bicycling magazine.

The magazine teamed up with Trek in a three-month experiment to see how the use of a new bike would affect the lives, health and daily routines of the 50 recipients.

Ranging in age from 13 to 73, they were selected from among more than 200 applicants in an essay contest. They were looking for a way to lose weight, get healthier, conquer fears, save transportation money or spend more time as a family.

The magazine calculated that the 50 participants rode a total of 11,742 miles and burned 751,841 calories. They had 14 flat tires. None of the bikes was stolen.

Its survey of the 50 riders found that bicycling had an impact on their lives: 64 percent felt healthier, 54 percent felt more independent, 34 percent felt more productive at work or school, and 72 percent said cycling improved their relationships.

The magazine said it chose Portland as “Bike Town U.S.A.” because it is a bicycle-friendly city with bike lanes on roads, bike trails and manageable traffic.