They do run a fair bit: they lead and form options for players kicking into the dangerous forward line. But they wouldn't run as much as the average center man.
During the 2009 Grand final broadcast, a commentator stated that St Kilda captain, Nick Riewoldt, who leads and presents from the forward line, was 'measured' at covering about 3.7 Kilometres [just over 2.3 miles] per game. Of course, that is not flat even running: it includes considerable stop-start, weaving, change-of-direction and pace and leaping for the ball. Overall, the actual strain on the muscles might be equal to nearly 10 kilometres!!
Of course, this is not characteristic of a forward, as Nick Riewoldt is known for his tremendous work-rate, and Geelong played 3 players on him during the course of the final - which worked!
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