Last Updated: Friday, 20 April 2007, 14:27 GMT 15:27 UK
Analysis of a marathon runner
36,000 runners of all abilities will be taking part in the London Marathon on Sunday.
But do 26.2 miles have a marked difference to those at the elite end of the race as compared to a club runner?
BBC Sport spoke to the English Institute of Sport, Great Britain's Kathy Butler and Scottish club runner Rachel Fagan to see what sort of physical and mental imprint the world's biggest race will have on them.