“…Laboratory studies have occasionally examined human locomotion of a few subjects over days or months (Aschoff et al, 1967; Chandrashekaran et al, 1997; Endo et al, 1999; Gander et al, 1986; Kriebel, 1974; Natale, 2002), and use of ambulatory accelerometer technology more recently has made it possible to monitor the activity of individuals living natural lives for a year or longer, but again with a limited number of subjects (Binkley et al, 1990; Yoneyama et al, 1999). Surveys of sleeping habits have been conducted in numerous countries (Giannotti et al, 2002; Hébert et al, 1998; Horne & Östberg, 1977; Jean-Louis et al, 2000; Laberge et al, 2000; Park et al, 1997; Refinetti, 1995; Roenneberg et al, 2003), thus allowing a gross comparison of activity times around the world, but without real-time resolution.…”