"there is a shortage of skilled labor in this field"
"his labor did not require a great deal of skill"
"she was in labor for six hours"
"he prepared for great undertakings"
"She tugged for years to make a decent living"
"We have to push a little to make the deadline!"
"She is driving away at her doctoral thesis"
"She was digging away at her math homework"
"Lexicographers drudge all day long"