Sweating Experts say that in order to be healthy, you really do need to break into a sweat when you exercise.

Official advice that 30 minutes of gentle exercise a day is enough to improve your health has been revised by the scientists who first developed the international fitness guidelines. Members of the American College of Sports Medicine are concerned the advice is being misconstrued.

Some may take this to include a mere stroll to the car. People should do at least 30 minutes of moderate exercise five days a week, or 20 minutes of vigorous exercise, like jogging, three days a week, they say.

There is confusion about what is the ideal amount and intensity of exercise to improve health. All agree that regular exercise is essential. The World Health Organisation (WHO) has said 30 minutes of gentle exercise each day could be enough to sustain a minimum level of fitness.

Recently, researchers at Queen’s University, Belfast, found walking for half an hour on just three days a week gave similar fitness and blood pressure benefits to walking for 30 minutes five times a week.

The sports scientists, however, say this advice is misleading and could encourage people to do too little exercise. “There are people who have not accepted, and others who have misinterpreted, the original recommendation.

Some people continue to believe that only vigorous intensity activity will improve health, while others believe that the light activities of their daily lives are sufficient to promote health,” they told Circulation , the journal of the American Heart Association.

Their original recommendations in 1995 were quickly adopted by the WHO. They now stress that adults need to top up their routine activities, such as casual walking and housework, with structured exercise.

This should include vigorous (jogging) and moderate aerobic exercise (a brisk walk), as well as twice-weekly activities, such as weight training, which maintain or increase muscular strength and endurance.

People can do short bouts of exercise to count towards their weekly goals, but these must last for at least 10 minutes. They say that even more exercise than this may have further benefits.

However, research has also shown that too much exercise can be damaging to the body.

“People who are very overweight would have to do an hour of exercise a day just to maintain their weight if they aren’t going to change their diets,” he said.