People were 'straining their necks' [=were lifting their heads as high as they could by stretching their necks] to see the fight.
He 'cracked/collapsed/buckled under the strain'. [=he was not able to deal with the pressure]
I 'strained my ears' to hear [=I tried very hard to hear] what they were whispering.
(..) in the ground down there. They're just falling into it. Silver mines, gold mines, tin mines. Payrolls so heavy we'd strain ourselves stealing them. You just keep thinking, Butch. That's what you're good at. Boy, I got vision, (..)1969 Butch Cassidy and the Sundance Kid