Leading sports doctors have strongly criticised the way PE is being taught in English schools.
Experts say many children do not get a proper workout which helps them develop coordination, strength and agility.
The British Association of Sports and Exercise Medicine wants all schools to use a short exercise routine called "five-in-five".
But the government said PE was a matter for individual schools.
Specialists in sports and exercise medicine say that too often PE lessons focus on developing sports skills rather than encouraging flexibility and movement.
The British Association of Sports and Exercise Medicine (BASEM) has endorsed a quick training programme designed to address this.
Five-in-five provides five exercises in five minutes. A leading international sports coach, Kelvin Giles, has devised more than 20 five-minute routines.
He has worked with elite sports men and women around the world, from athletics and rugby to football and tennis.
He also spends a lot of time in schools, and said PE lessons in the UK do not give children a proper workout.
"Out of the 40 minutes there's eight minutes of activity going on. Very often the kids are standing around and just listening to the teacher talk. So heart rates aren't being raised. Mechanical efficiency isn't being looked at."
As a result, he says, the level of fitness in most children is "catastrophic".
The five-in-five routines involve squatting, lunging, pushing, bracing and rotating.
"You can get stronger, you can get more stable, you can have a much better posture, by exposing yourself to five minutes a day," said Mr Giles.
The initiative has won the backing of the UK's leading sports doctors. To mark its annual conference in London, the British Association of Sports and Exercise Medicine has called on UK governments to incorporate the programme in all schools.
The Association's chairman is former Olympic gold medallist rower, and chief medical officer for the London Olympics, Dr Richard Budgett. He is deeply concerned about PE in schools.
"If you're not a natural athlete, not attracted to sport and exercise, there is a real problem. It's very easy to drop out."
"By using a programme like five-in-five in schools we can get young people with the skills that they can then use as they get older. So they can keep fit, keep their joints working properly and prevent all sorts of diseases, from osteoarthritis through to diabetes and heart disease."
The Department for Education in England says it will be up to schools to decide if they want to adopt this.
It wants them to focus more on competitive sport. Sports physicians say five-in-five will help gifted children to excel, while ensuring all receive a proper physical education.