INVESTIGATORS have begun two large studies of stretching, asking about its effectiveness in much the way scientists might ask about a new drug or medical device. They’re actively recruiting thousands of volunteers to participate, in the United States and elsewhere, and randomly assigning participants to use the method, or not. That is the only way, researchers say, to detect the subtle effects that most treatments and exercise interventions might be expected to evoke.

The studies are being done independently, one by researchers based in Norway and Australia and the other by a group in the United States.

The studies are not identical, reflecting perhaps the different views of stretching worldwide. People in Norway and Australia stretch for different reasons than people in the United States and do slightly different stretches. Yet exercisers and coaches everywhere, the researchers report, tend to have passionate convictions about the merits of stretching, or lack thereof.

Researchers say those strong feelings pro and con show in themselves that it will take a large study to see what, if anything, stretching really accomplishes. If stretching were remarkably effective, athletes would notice its effects right away and everyone would agree on when to stretch and what stretching does.