The Crowd at the Olympics - who or what are they really?

I have just seen Andy Murray play like a possessed and talented demon and thrash Roger Federer in the Olympic Gold medal tennis match. In the immediate post match interview Sue Barker rather predictably asked whether the crowd helped him? Was the crowd like an extra man, she lamely asked?
The 'crowd being an extra man' thing has come from the commentators of the rowing regatta at Eton Dornay - the influence of the very loud crowd there having the same effect as that of an extra rower in the boat! But in tennis? Surely Sue Barker should have said an extra arm, an extra leg for Mo Farah, an extra leg & arm for steely but cute Jess Ennis and an extra sail for Ben Ainslie!