Why is the sling-shot bowling action so effective?

The sling-shot action stands out in fast bowling history due to a rare conjunction - unconventional style and outstanding records. This method has proved to be the downfall of batters ever since Aussie legend Jeff Thomson jettisoned bowling traditions and came up with the unusual bowling action.

In this method, the bowling arm goes backward like a slingshot instead of coming round from behind. The stored elastic energy of the bowler's upper body muscles then translates into the maximum speed of the ball upon release. The arm, therefore, appears to slingshot like an elastic band.

But what makes this action so effective in fast bowling?

A general explanation could be that bowlers with the sling-shot action take advantage of batters' pre-disposition to look for the ball in a particular area (the high-arm action). While facing slingers, batters find it difficult to estimate the length of the ball due to the low point of release.

This is an important variable in fast bowling. A higher release point extracts more bounce while a lower release point generates less bounce. The batter then changes his/her approach accordingly. However, this predictability goes for a toss when the ball is in the hands of a slinger.

One of the best exponents of the sling-shot action, Lasith Malinga had a low point of release. But this did not necessarily convert into less bounce. Malinga created a disjunction between the ball's point of release and the bounce, which kept batters guessing.

However, such non-conformism is fraught with risks: sling-shot bowlers find it tough to ensure that the ball will land on the seam and not on the shine and vice versa. So why risk a slinger when there are other bowlers around with a more 'regular' fast bowling action? The answer is extra pace.

Bumrah is one of India's fastest bowlers.

Team India fast bowler Jaspreet Bumrah's speed could be attributed to his sling-shot action. Bumrah has a deceptively short run-up. So did Mitchell Johnson, one of Australia's fastest bowlers. Their run-up would give no indication of the terrific pace with which the ball would travel after leaving the arm, thanks to their slinging action.

How do sling-shot fast bowlers then generate extra pace?

The answer is the delayed bowling arm, which is a vital aspect of sling-shot fast bowling. This requires proper sequencing of the bowler's body so that physical attributes can be mobilized to create extra speed.

Mitchell Johnson's delayed arm action often caught batters unawares.

The crucial moment here is between the front foot landing and the chest drive. As the chest drives forward, the bowling arm has to lag behind momentarily before moving forward like a sling-shot. A little bit of bio-mechanics might be useful here.

To maximize the elastic force of the arm, the draw length has to be maximized (the distance between the upper body and the bowling arm). Delaying the arm ensures maximum draw length and the stored elastic energy of the arm then translates into the maximum kinetic energy of the ball.

The delayed arm tactic, therefore, turns the fast bowler's upper body into a human sling-shot and helps generate significant speed.

An unpredictable length coupled with extra pace certainly makes for a lethal combination and the sling-shot action provides bowlers with both. It is no wonder that slingshot bowlers have left an enduring legacy in the annals of fast bowling.