"Look at the athleticism of our players now, we are starting to raise the bar in that area," the manager told the BBC ahead of Monday night's friendly against Austria at Stadium MK. "We are a very different team to where we were 12 months ago.
"We want to be the fittest team in the world. The players are working hard in that area. But we're nowhere near where we need to be.
"We've got a lot of work to do between now and 19 July to make sure we arrive at the European Championship physically ready."