The study conducted by researchers from the University of Exeter and Brunel University found that an alarming percentage of Brits think that moderate exercise is good.
They also said that the trend is worrying when most studies have proved that the greatest health benefits are derived from regular participation in vigorous activities, such as jogging and competitive sports.
"Time and time again, the largest and most robust studies have shown that vigorously active individuals live longer and enjoy a better quality of life than moderately active individuals and couch potatoes. 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.
The challenge now is to amend Britain's physical activity guidelines so that they emphasise the role vigorous activity plays in fighting obesity, type 2 diabetes, and heart disease," Dr Gary O'Donovan, exercise physiologist from the University of Exeter and lead author on the paper said.
In addition to halving the risk of diabetes and heart disease, recent studies have shown that regular exercise offers protection from certain cancers. The research team believes that 30 minutes of brisk walking per day might be sufficient to reduce the risk of breast cancer, but regular participation in vigorous exercise is probably necessary to reduce the risk of prostate and colorectal cancers.
The researchers argue that in order to enable the public to make fully-informed decisions about exercise, policymakers should describe the dose-response relationship between physical activity and health. Dr. O'Donovan explains that: "Brisk walking offers some health benefits, but jogging, running and other vigorous activities offer maximal protection from disease."
"Sedentary adults should complete a six- to twelve-week programme of moderate exercise before beginning a programme of vigorous exercise. Men older than 45 and women older than 55 should consult their GP before taking up vigorous exercise," Dr. O'Donovan added.
The research is published in Preventive Medicine.