mattyv

This topic is in need of some logical scrutiny, particularly given the recent developments with New Zealand in Australia. A seemingly simple question needs to be answered. What exactly is a throw?

Before we try to answer that question, I will declare my biases. I am Australian, a fan of Shane Warne’s bowling, and also enjoy watching all out quicks like Shaun Tait and Lasith Malinga. Having said that, I will try my best to stick to the facts, and use Murali only as a necessary comparison.

A traditional overarm throw

Dictionary definitions of throwing don’t accurately define the elbow movements (the point of contention here) in any way. We must turn to biomechanics to find our definition. Even then, the answer can’t be one sentence long.

Baseball is typically a good place to see an example of a quality throwing action.

Figure 1. The three phases of an overarm throw (Hamill, 2003).

The pertinent movements to this discussion occur during the Cocking and Acceleration phases as shown in Figure 1. The elbow undergoes a period of flexion in preparation for the throw, then rapidly extends through acceleration for maximal force summation upon release.

Figure 2 again shows the elbow moving from a flexed position into extension through the forward motion, releasing at a point of full extension.
Figure 2. Overarm throw as applied in a baseball pitch (Hamilton, 2002).

Hamill (2003) also notes that the Brachialis and Biceps Brachii are highly active in deceleration, minimising hyperextension.

Alright, so now we have a basic idea of what makes a throw, a throw. Cocking of the arm, flexed at the elbow, then forceful extension to the point of release. Flexion -> Extension.

Fast Bowler’s Action

Obviously, bowling has some major differences to throwing, but the above can be compared with different bowling actions to see if they match up in key areas. From the super-slow footage we keep seeing (and people tout as evidence of fast bowler “chucking”), the elbow movements can be analysed in a reasonable amount of detail. We don’t have digitised representations, so we’ll have to use our eye for this one.

Assuming a right-handed bowler, let’s use the point where their left hand reaches the peak height of its motion before being pulled down towards the body as our reference point for the transition from the Cocking phase to the Acceleration phase. This area just before transition to the Acceleration phase is shown in Figure 3.

Figure 3. Bowler just before acceleration phase of action (LaHood, 2000).

After this point, we see rapid acceleration of the right arm, coupled with full-extension of the elbow. This level of elbow extension is reached well before the point of ball release. That is our first significant difference with a throw.

As the arm approaches the point of release, we see the section of controversy. Extremely fast bowlers (and possibly others) exhibit an often pronounced hyperextension of the elbow, followed by a return to full extension (relative flexion) on or just after release. Is this a throw? If a throw is an overarm action as described by biomechanists, then no, this is not a throw.

Cocking of the arm, flexed at the elbow. Forceful extension before the point of release, passive hyperextension then relative flexion to the point of release. Flexion > Extension > Hyperextension > Relative Flexion.
Fundamentally different.

Spin Bowler’s Action

Here we will find some similarities and some differences compared to a throw. How much similarity depends on the bowler.

A typical spin bowling action involves the following elbow movements:
Flexion pre-acceleration > extension, but with maintenance of a flexed position overall > position held to point or release.
Or…
Flexion pre-acceleration > extension to fully extended position > position held to point of release.
As has been shown by expert video analysis of many bowlers, there is always a degree of deviation within these movements, usually of a matter of a few degrees. What’s missing to make these into throwing actions is the use of active (significant triceps brachii involvement) elbow extension adding the last (technically 2nd last) part of propulsive force to the point of release.

A less typical spin bowling action involves the following elbow movements:
Flexion pre-acceleration > extension throughout acceleration to the point of release. What’s more, it would appear (without EMG data to back this up) that the triceps must play a significant role in this action. Without that, the rate of elbow extension late in the action would not be possible.

Returning to Hamill (2003), triceps brachii is among the largest contributors to the Acceleration phase of a throw, along with the anterior upper limb adductors and some of the shoulder stabilisers. The conclusion is, the less typical spin bowler’s action has several key similarities with a correct throw, that are missing in the other spin bowling actions. The person of reference for this non-typical action goes without saying.

Summing up, the bowling actions seen in many fast bowlers, whether they hyperextend or not, are not consistent with what human movement would define as a throw. In general terms, the same applies for spin bowling actions, the muscle activity and elbow movements during the Acceleration phase don’t fit those of the throw. The method of putting linear or angular acceleration on the ball is the whole point of allowing certain actions, and disallowing others. This is why one famous spin bowling action not only fits in with the definition of a throw, but also contravenes the thinking behind the rules.

But I don’t care, let him bowl. All I want is for people to know what they’re saying when they accuse someone of “throwing” or “chucking”, because quite often they are fundamentally incorrect, letting emotion guide them rather than facts. My analysis may have partially gotten some bowlers off the hook through mere linguistic technicality, but if so, then it’s time for a change of terms.

References

Hamill, J., & Knutzen, K. (2003). Biomechanical basis of human movement. (2nd ed.). USA: Lippincott Williams & Wilkins.

Hamilton, N., & Luttgens, K. (2002). Kinesiology: Scientific basis of human motion (10th ed.). NY: McGraw-Hill.

LaHood, L. (Ed.). (2000). Coaching youth cricket. Australian Cricket Board. South Australia: Human Kinetics.