Children in the Republic are not as physically active as children in Northern Ireland, according to a study by Dr Catherine Woods of DCU.
Dr Woods said her research showed children from the south had less aerobic capacity and were unable to run as many laps as children from the North.
Addressing a conference on childhood obesity in Letterkenny, Co Donegal, Dr Woods said 80% of children in the south were not as active as they should be.
Dr Pat Wall of UCD expressed concern at the lack of playground activity in schools.
Dr Wall said litigation against schools meant children were often not allowed to run, had no skipping ropes or hula hoops and added that the most active exercise among some children was text messaging.
