MIKE PERRY, a 31-year-old rower, trained by himself in Ann Arbor, Mich., for six years while his wife attended medical school. Now he is a member of the United States rowing team and hopes to be selected in a couple of months to compete in the Summer Olympic Games.

These days, he works with a coach and a team, and for the first time he is also going to a gym twice a week and lifting free weights for his upper and lower body, and doing a lot of core exercises, he said. His coach insists upon it. Mr. Perry, though, said he cannot tell whether weight lifting is helping his performance.

His 29-year-old teammate, Mark Flickinger, thinks weight lifting has helped him. He said it is difficult to distinguish between the effects of training by rowing on the water and weight lifting at the gym.

But, he added, after three years of working with weights  including lifting to failure, the point at which he cannot do another repetition  he has become a better athlete. The training “improved my P.B.’s by a substantial margin,” he said, referring to personal bests, his best performances.