While riders will enjoy to sleep a little longer than usual (if not awoken by the UCI "vampires" for some early blood controls), the term rest day is a bit misleading. Most every team will have a press conference and the riders, especially the top contenders and stage winners like Michael Rasmussen, will be sitting through some Q&A with the press.
Riders would likely rather rest completely than having to do the media stunt, but it is of course good for their and the sport's exposure. But besides those little distractions of the rest day, the riders will actually ride. Not too long, maybe an hour or two, and mostly relaxed.
But it is vital to keep the blood flowing. Having raced intensely for one week, then stopping completely for a day and then starting again, the body will scream in pain, having expected that the suffering is over.
Former polka-dot Stéphane Augé of Cofidis described what his day will look like in an interview with velo101.com and confirms that the day starts out a little quieter, with a "lazy morning, then a bit of training for an hour or two." He mentions that it is essential to recuperate, decompress and walk around a bit, "not just sit on the phone all day."
Those who have no ambitions for tomorrow's hilly affair will likely take it a bit easier on the rest day than those who actually want to contend for victory. A typical route on a rest day may include a stop at the local coffee shop stop or a nice, cooling ice-cream to help fight the high temperatures of the last days and give the brain a little reward.
Of course with using less energy throughout the day the racers will have to make sue they don't overeat and pay big time on their way up to Briançon.