What makes Test cricket's best spin bowler so effective?
With a victory over England in the fourth test by an innings and 36 runs, India's cricket team have secured their fifth consecutive test series win and have now gone over four years without losing a test match on home soil - a run of 18 matches. Throughout this period we witnessed the meteoric rise of Ravichandran Ashwin, India's prize test match finger spin bowler.
Ashwin, now the number one ranked bowler in world cricket has amassed 15 five-wicket hauls in tests, the highest for any bowler in two successive calendar years. In September he became the second-fastest bowler to claim 200 test wickets in his career.
Statistics aside, success on the world stage is not a matter of chance, quite the contrary. Ashwin's journey is a culmination of his technical refinement, innovation and the teammates who bowl alongside him.
Refining the technique
While there are many facets that contribute to a successful spin bowler, imparting a high number of revolutions on the ball is seen as critical and the main cause for both the ball's "drift" in the air and deviation off the pitch. Coupled with the ability to pitch the delivery in advantageous areas, elite finger spin bowlers such as Ashwin play an integral role in the success of teams competing in the international game.
A forthcoming study on the biomechanics of elite finger spin bowling, led by myself and my colleague, Mark King, at Loughborough University in conjunction with the England and Wales Cricket Board, profiled 30 elite male finger spin bowlers over a four-year period (including the English spinners Graeme Swann, Monty Panesar and James Tredwell). Our team of researchers explored the technical factors within a bowling action that influence the rate at which a ball spins.
The team observed very strong positive relationships between the orientation of the bowler's pelvis and the rate at which the ball spins during flight, particularly at the instance of front foot contact and ball release. These findings created a compelling argument that highly advanced motions of the pelvis are paramount to producing high spin rates to the ball and therefore that spin bowling should not be solely thought of as an upper arm skill.
The movement during the ball's flight is due to its "lift" or Magnus force, which affects the way a ball reacts during motion. This movement occurs because on the side of the ball which is advancing due to the spin motion the air flow is slowed down, creating a high pressure region. On the other, receding side, it creates a low pressure region. The difference in pressure causes a "lateral" force perpendicular to the ground and a lateral movement of the ball during flight. This is known as drift.
The force of the lift will vary in direction and magnitude and depends on the amount of spin and the axis along which the ball is spinning. In addition, cricket balls have a seam, and spinners commonly apply spin along the line of this seam to help their grip on the ball. This means the spin axis is commonly kept perpendicular to the direction of the seam, promoting a stable seam position and the possibility of the ball deviating off the seam the moment it hits the pitch.
When the ball meets the pitch surface, particularly in India (due to drier pitches creating high friction between the ground and the ball), this commonly creates large lateral deviation and a heightened challenge to the opposing batsman.
Coming back to Ashwin, since 2012 he has noticeably made a number of key technical changes to his bowling action to improve alignment and promote a transfer of momentum throughout his delivery stride. In 2016, he now bowls with a slightly open pelvis orientation when his front foot hits the ground. This differs to the strictly side-on, or at times closed-off pelvis orientation that he used when releasing the ball back in 2012. He now has the ability to rotate his pelvis effectively and efficiently, promoting the transfer of kinetic energy from the pelvis to the hand as he releases the ball, and so injecting greater spin onto the ball.
Partnerships and pace
Humility is a strong virtue in any individual. With this in mind, Ashwin's rise to stardom has to be partly credited to his orthodox left arm spin partner, Ravindra Jadeja.
Between November 2015 and the end of the fourth test against England in mid-December 2016, India's star duo had accumulated the most wickets in test cricket - an incredible 124. The pair are unrelentingly accurate, with Jadeja mounting great pressure, bowling 53 maidens (an over, or six consecutive deliveries where no run is scored) in the current series against England alone.
The speed at which the ball is released also plays a significant role in the success of an elite spin bowler. When a new, competent batsman enters the crease, they use the idiosyncratic cues provided by the bowler, such as the release velocity, height, and angle of preceding deliveries. This forms a mental template of the ball's trajectory - essentially an attempt to predict the trajectories of the deliveries to follow.
Here, Ashwin's subtle variation of the speed and the axis around which he spins the ball comes into play. He commonly delivers his stock ball with an initial release speed around 54mph. Variations of pace close to this speed may exploit a batsman's mental template and take advantage of the batsman's subtle "blindness" to length and speed. This can create a fatal weakness in judgement, particularly for any new batsman at the crease.
The new batsman's ability to tell what speed and trajectory the ball will arrive is now sub-optimal, meaning vital mistakes are made in deciding whether to come forward or back when playing the ball. This can result in a quick return to the dressing room.
Ashwin can also be considered as one of the modern game's great innovators through his use of a unique delivery known as the "carrom" or "sodukku ball", meaning "snapping of fingers" in the Tamil language.
When delivering the carrom ball, Ashwin spins the ball using half as many revolutions as he would with one of his regular deliveries. The ball is released out of the front of the hand as opposed to the side, using the middle digit to impart spin. As a result it is very difficult for the opposing batsman to distinguish and therefore a dangerous tool of deception.
With this magnitude of spin, the ball's trajectory is much straighter and results in many wickets as the opposing batsman often plays down the wrong line of trajectory. As a result, Ashwin, who is one of the very few operators of this delivery in the world game, has one of the highest percentages of dismissals for leg before wicket in test cricket to date.
All this has combined to make Ravichandran Ashwin one of the most effective bowlers in today's modern game.