Biomechanics and the Art of Bowling

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Biomechanics and the Art of Bowling

Dr Rene E. D. Ferdinands   


There is little doubt that the great diversity of styles and techniques of bowlers from countries enjoying test match status has helped to shape the history of cricket. With the recent world-wide implementation of professional coaching schemes, which generally teach only one, or perhaps two optimal ways of delivering a ball, bowling could be in danger of losing its technical diversity. Are we therefore on the verge of a new era in which the art of bowling is irretrievably lost? Possibly! However, as discussed below, the biomechanical principles underlying the bowling technique reveal some interesting new facts.

For those less well acquainted with the game of cricket, the technique of bowling must seem exceedingly simple. Just use a straight arm to release a ball at a suitable speed to cover a distance of 22 yards bouncing only once off the ground before reaching the batter. If so simple, how could the execution of such an action in a cricket match hold the attention of millions of people for 3, 4 or 5 days at a stretch? And why would particular individuals, called bowlers, spend countless hours perfecting their art in the practice nets, only to spend countless more hours on the cricket field, often under the most trying of conditions, to deliver balls at a stationary batsman?

Those who know the game intimately are aware of the reasons for such rigorous practice. Bowling is an art of infinite subtlety, not only in strategy, but also in its most basic mechanics. The bowler has an almost unlimited array of variations to help confound the batsman - from varying the pace, the length (the distance travelled before bouncing), and the line of delivery, to swinging and swerving: motions dependent on the intricate combination of the seam angle and spin of the ball as it travels through the air. A further degree of complexity is introduced when the seam angle and spin are also used to change the line of the ball off the pitch.

It is evident then that the physics of bowling is immensely complex, and not fully understood. In this article, only one aspect of bowling is discussed, the one that is probably the most important: the biomechanics of bowling. Some coaches believe that the mechanics of bowling is relatively simple, and that the basic side-on action is the optimal technique. However, a proper understanding of the biomechanical principles underlying bowling reveals that this is in no way the case.

The Basic Bowling Technique

For those not familiar with cricket, a brief account of the basic bowling technique (right-hand bowler) will serve as a useful introduction (Fig. 1).

After a run-up to generate momentum, the bowler leaps into the air with the back arched, and the head behind a high left arm, which is bent towards the right shoulder. The bowling arm (right arm) at this stage is bent and close to the body with the hand about face level, and the trunk leaning backwards and laterally. Then as the right foot contacts the ground, the straightening of the left arm is synchronised with that of the bowling arm as it drops towards the level of the hips. Once the bowling arm is fully straightened ("locked"), the left arm is pulled downward facilitating the circular swing of the bowling arm about the shoulder joint as the trunk begins to flex forwards. This process continues until the ball is released off the left foot, and the "follow-though" is initiated when the bent right leg steps past the front leg.

Figure 1: The basic bowling technique (right-hand bowler) has many characteristics: the run-up, leap, right foot contact, left arm motion, bowling arm rotation, left foot contact, ball release, and follow-though. A good technique allows the bowler to deliver a ball with speed at a chosen point on the pitch while maintaining a straight bowling arm [Picture from Biddle et al., 1991 - Courtesy of the Crowood Press, Ltd].

Models of Bowling

It appears that much of the cricket literature on bowling technique is generated purely from the experience of past players. Though there has been some excellent research into the biomechanics of injuries sustained by fast bowlers, most other attempts to understand the biomechanics of bowling have been limited to the analysis of kinematic and force plate data. This has played a part in the development of the bowling technique, but is inadequate to understand the underlying mechanics of bowling. The University of Waikato (Dept. of Physics & Electronic Engineering, and Dept. of Mathematics), Hamilton, is now generating the first mathematical models of bowling in an attempt to understand bowling techniques and thus improve coaching methods. A physical action, such as bowling a ball, is often difficult to understand if considered throughout in all its complexity. On the other hand, a simplified model of the event is much easier to study and understand. Thus, the human body can be represented as a system of interconnected rigid body segments subject to applied external forces and torques. A segment could be, for example, a forearm, a thigh or any other major body part attached by a hinge to others (Fig.2).

There are two general approaches of rigid body modelling within the field of classical dynamics: the direct method of analysis by applying Newton's laws to each of the individual parts of the system; or a more indirect method, which treats the system as a whole by using a comprehensive theory of mechanics based on energy principles. This latter method is known as Lagrangian mechanics, and can often be used to formulate a complete set of ordinary differential equations for the motion without solving explicitly for the constraint forces acting on the various parts of the system. It is characterised by its simplicity and is applicable in any suitable coordinates.

Figure 2: A multiple segment, Lagrangian rigid body model of bowling.
Inset shows how the system can be actuated by a selection of joint torques,
Ti, and choice of initial values for the generalised coordinates, qi..

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