"Misleading" government guidelines have led to many Britons wrongly believing that moderate exercise is as beneficial as a vigorous workout, a study alleges.
People shouldn't believe that this will do, the report chides
In a survey of nearly 1,200 people, around half of men and three quarters of women thought moderate exercise conferred the greatest health benefits.
Guidelines urge 30 minutes of moderate exercise each day five days per week.
But the authors of the study, published in Preventive Medicine, said vigorous exercise was best for averting disease.
The NHS guidelines say "taking a brisk walk, spending some time doing the gardening or doing a few laps of the local swimming pool on the way home from work" can all improve health.
But the researchers from Exeter and Brunel Universities said these activities were unlikely to do much for them.
"It's extremely worrying that British adults now believe that a brief stroll and a bit of gardening is enough to make them fit and healthy," said Dr Gary O'Donovan, lead author.
"Brisk walking offers some health benefits, but jogging, running and other vigorous activities offer maximal protection from disease."
Other specialists said the survey results were not surprising, and that few people in any event met the guidelines for moderate exercise.
But Paul Gately, professor of exercise and obesity at Leeds Metropolitan, said it was very difficult to formulate a "one size fits all" policy to exercise, as moderate exercise for one would be intense for another.
Light: You can talk at the same time
Moderate: Makes you slightly breathless
Vigorous: Makes you breathe rapidly
He also stressed that public misunderstandings about exercise could not be blamed solely on the government, as academics themselves were continually formulating new theories.
In August alone two separate and apparently contradictory reports emerged.
One found walking less than the current guidelines stipulated had significant health benefits; another suggested a minimum of 20 minutes of vigorous exercise three times a week was needed for good health.
In addition, no-one is clear what part exercise really plays in preventing disease.
While some studies have shown that those who workout may have a reduced cancer risk, it can be difficult to separate this from other lifestyle factors like diet, alcohol and tobacco consumption, and socio-economic group.
A Department of Health spokesperson said its guidelines were "based on a comprehensive review of the evidence, carried out by a team of academics and expert advisers.
"We take a keen interest in new developments in this area, but there are no plans at present to change the existing recommendations for adults."