The New York City marathon is less than two weeks away, and many of those planning to compete in it may now be embarking on long practice runs. As a result, it’s busy season for the physical therapists and exercise physiologists at the U.S. Athletic Training Center in Midtown. The fitness and physical therapy center is home to a year-old “gait analysis laboratory” that helps runners correct the imbalances that can slow them down, and cause injuries.

Three days before last year’s ING New York City Marathon, Brazilian runner Marilson Gomes dos Santos turned up at the training center limping in pain. “He was thinking of dropping out,” the Upper East Side sports podiatrist who referred Mr. Gomes dos Santos to the laboratory, John Connors, recalled.

At the laboratory, a veteran physical therapist and co-owner of the training center, Gary Guerriero, and Mr. Connors scrutinized the distance runner’s stride, instructing him to make small adjustments that could reduce the inflammation of a tendon on the bottom of his foot. On race day, Mr. Gomes dos Santos completed the 26.2-mile course in two hours, nine minutes, and 58 seconds, making him the first South American in history to win the New York City marathon.

He phoned Mr. Connors from the finish line to say, “Thank you.”

In the laboratory, cameras are positioned in front of, behind, and alongside a treadmill, on which clients run for about 20 minutes. A $300 gait evaluation, which lasts 1.5 hours, also includes an assessment of an athlete’s strength, flexibility, and alignment when standing by a physical therapist and an exercise physiologist.

The treadmill video recording is examined by training center staffers (and, sometimes, by Mr. Connors), who check for any inconsistencies, such as the pronounced inward rotation of the feet, or the lack of joint alignment. To correct such conditions, the staff may prescribe an orthotic shoe insert, a foot wrap, or a series of corrective exercises. Athletes are also given a copy of the laboratory recording so they can detect possible problems with their positioning. “Dancers are used to looking at themselves in the mirror; runners are not,” a co-owner of the 13-year-old training center, Mary Leonard, said. A former jazz dancer, Ms. Leonard noted that clients are often surprised to see how much they favor one side.

“The body is a great compensator,” Mr. Guerriero added. “When there’s an issue, the body will try to balance out the problem, by compensating on the other side.” That puts strain on the counterbalancing side’s joints, tendons, bones, and muscles that, if left untreated, could result in serious injuries, according to Mr. Guerriero. He said, ideally, runners would seek a gait analysis prior to beginning marathon training — or a less intensive running regimen, as it may be — but most clients come to the laboratory only after experiencing pain or suffering an injury. In the four to six weeks leading up to the marathon, Mr. Connors said he sees “a drastic increase” in the number of patients seeking relief from running-related aches and pains, or perhaps more serious injuries. “The body usually breaks down right before the marathon,” he said.

Sometimes, Mr. Connors advises his patients to withdraw from the race; other times, he refers them to the training center laboratory. For Mr. Gomes dos Santos, that apparently made all the difference.

The U.S. Athletic Training Center, 515 Madison Ave. at 53rd Street, 212-355-8440.