Union leaders are concerned at reports that children as young as three could face two hours compulsory exercise a week.
Plans could see compulsory exercise at nursery school
Nursery nurses' union Unison and teachers' union EIS said other subjects could suffer if the reform was implemented by the Scottish Executive.
A Sunday newspaper claimed an expert group appointed by the executive would force children to take PE lessons.
An executive spokesman said the report was being studied and an announcement would be made shortly.
Striking nursery nurses
The Physical Education Review Group was set up following a report last June from a task force which
recommended that all pupils should receive a minimum of two hours quality physical education in school per week.
But Unison official John Stevenson said his nursery nurse members would have
concerns about the plans.
Mr Stevenson is the Edinburgh branch secretary who earlier this week announced that striking nursery nurses in the capital had agreed to return to work.
He said problems might arise if nurseries were told to set aside half a day for PE instead of integrating it into lessons as they saw fit.
"One thing I have learned throughout this strike is that politicians are
ignorant about what's going on in nurseries," he said.
And EIS general secretary Ronnie Smith said: "What gives way to create a
space for this?
"Many children commonly attend nursery for half a day and if there's going to
be a significant amount of PE this doesn't leave an awful lot of time for
everything else. It's about finding a balance."
He added: "I worry about any ad hoc sticking plaster approach to particular
problems. Obesity is not just about exercise, but also diet and everything
A Scottish Executive spokesman said: "The executive is committed to tacking
obesity and school sports will play an important part in this.
"Ministers have received the report from the Physical Education Review Group
and are currently studying it. We hope to make an announcement very shortly."