You use legwork to refer to work that involves physical activity such as interviewing people or gathering information, especially when this work forms the basis of other, more intellectual work.
He assisted in unofficial ways with the routine legwork in various investigations.
legwork in British English
(ˈlɛɡˌwɜːk)
noun
informal
work that involves travelling on foot or as if on foot
legwork in American English
(ˈlɛgˌwɜrk)
US
noun
Informal
routine work that is necessary to a job, as that of a news reporter, involving, typically, walking or driving from place to place, away from the office
Examples of 'legwork' in a sentence
legwork
Preparing a whole crab requires legwork but is hugely satisfying.
Times, Sunday Times (2014)
Buyers looking for holiday homes in the countryside will have to do a little more legwork.
Times, Sunday Times (2006)
So how much legwork on the pitch will you have to put in to burn off these drinks and snacks?
The Sun (2014)
It takes the legwork out of shopping in the capital by pulling together the best stores in one place.