At various points, there were 4 and 5 ball overs. The trouble with them is that it takes a long time to change the field at the conclusion of each over, which adds up to a lot of useless fooling around when you bowl 130 overs in a day. In a test match, eight balls without a break is a lot for a fast bowler to handle. So they came up with a system where after every over, instead of continuing straight away, the captain signals one or more batsmen who take their turn at number eleven. This leaves the fielders some time to get back into position before the next wave of power hits the pitch. The idea was to give the bowlers a rest every now and then so that they don't suffer from "overuse" injuries. It also allows the batsmen some time to recover between spells of play while still giving the game a finish. In fact, since its introduction in 1890, only two test matches have finished inside three days - both times due to rain delays - whereas five years ago, such a thing would have been unthinkable. Today's cricketers are a bit too obsessed with their own safety to think about coming up with new ways of playing the game. But if they were to do so, they might learn something from the people who played it before them.