Adam Clarke on Exodus 5:14

And the officers - were beaten - Probably bastinadoed; for this is the common punishment in Egypt to the present day for minor offenses. The manner of it is this: the culprit lies on his belly, his legs being turned up behind erect, and the executioner gives him so many blows on the soles of the feet with a stick. This is a very severe punishment, the sufferer not being able to walk for many weeks after, and some are lamed by it through the whole of their lives.