This could have been misleading, of course, but it looked to me as though he were straining hard.

Straining hard, he managed to get their body off the boulder.

He was straining hard, but the stob wouldn't come out.

The sun has been out for a while after straining hard through moody skies and my skin is warming.

She was breathing hard, straining hard, crying out in pain.

Max strained harder, wishing his wounds had not weakened him so.

He started to shove, his leg muscles straining hard.

Heather strained harder, trying to make them out.

Kevin strained harder against his ropes until they were cutting into him like wet rawhide.