How much is too little sleep?

... herself. She's up at 4:15 a.m., sees her first client at 5 a.m., gets in her own 90 minutes of aerobics and weight training before starting her shift at the gym. She also teaches fitness classes and tops off the day with an evening of softball or ...

http://www.argusleader.com/needlogin?type=login&redirecturl=http%3A%2F%2Fwww.argusleader.com%2Fapps%2Fpbcs.dll%2Farticle%3FAID%3D2013304140036%26nclick_check%3D1