Agreed with the above. I put mine on a mill at four and five months old. Some spin it, some do not but it gets them accustomed to it. The flirtpole and the walking is more of a game to them at the young age. When they are young you can introduce them to just about anything. Always be careful with things that can hurt their young teeth.
As far as a one year old I would say start light and work your way up on whatever exercise the dog does best. At one he/she should be able to handle a pretty decent amount of work. Walking is just about as safe as it gets. Use the spring pole/flirt pole til the dog says he is done and then do not force it. Let the gains be gradual. And there is no need to peak a dog for a long period of time. EWO