Elbow Angle for Legality of Bowling

Detection of Elbow Angle for Legality of Bowling Action in Cricket Using Bone Mean Detection Method

Abstract-This technique can be used to detect legal or illegal bowling actions in cricket by measuring elbow angle. A 30Hz camera can be used to record the movements of reflecting markers placed on the bowling arm during bowling actions while net practicing. Through the developed software, analysis of physical characteristics of the bowling arm can be monitored. Experimentally bone mean detection method gives 80-90% accurate angle to Elgon angle data with the advantage of automatic detection through image processing.

Keyword – Elgon, Bone mean detection, Image processing

1. Introduction

Although cricket is primarily supposed to be the game of batters but with the courtesy of advanced coaching techniques of bowling, the bowlers has played effective role to shape the outcome of various matches.

Definitely different styles of bowling create opportunities for the bowlers to discover different ways to bother the batter.

The biomechanical principles [1] defining the technique to deliver the bowl makes it easy to understand the art of bowling for those who are not familiar with the game according to which 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 [3].

Bowling is an art of infinite subtlety, not only in strategy, but also in its most basic mechanics [2]. The bowler may posses a number of ways to restrict the batter from scoring runs by varying speed (pace), length (the distance for the ball to be traveled before bouncing), line of delivery and swing/swerve of delivery which is relying on complex combination of seam (impression circulating as mid line at the exterior of the ball) angle and spin of the ball as it travels through the air [2].

2. Concepts

  • Law of cricket for legal action

International Cricket Council (ICC) makes the rules, In 2000 Law 24.3 it was decided that a ball is fairly delivered in respect of the arm if, once the bowler's arm has reached the level of the shoulder in the delivery swing, the elbow joint is not straightened partially or completely from that point until the ball has left the hand [3]. Otherwise it is termed as “chucking or throwing” giving the bowlers an unfair advantage to generate extra speed, however sometime due to inertial forces it is involuntary to control the straightening therefore, Ferdinands and Kersting suggested that a flat rate of 15º tolerable elbow extension be used. It was the first published laboratory study that examined elbow extension angle and accepted by ICC in 2004[4].

  • Identifying ROI

ROI is the portion of the bowler’s throwing arm in which the movement of the upper and the forearm to be described during each delivery.

  • Reflecting marker
  • We use three single color markers for the bowling a trial, 1st marker is circular to lateral and medial aspect of wrist, 2nd marker is circular to lateral and medial epicondyle of elbow and 3rd marker is circular to biceps and triceps muscles [5].

3. Our approched model

The camera was placed; face-on for front view and at for side-on on the path of the bowling action. The analysis was performed for the different bowlers during match and net practice conditions using model in fig 2. The bowling action was filmed and then converted into frames using Adobe Premiere [6]. The mode of detection used is the bone mean detection, detects the reflecting marker which is placed at anatomical position detailed in subsection 2.3 at the throwing arm and calculates the angle between the vectors of the reflecting markers shown in Fig. 1 and calculates it angle through Vector Analysis formula in Eq (i)

Finally sound interface and graphics user interface provide user friendly environment using Matlab [7].

4. Result and Discussion

Elgon is being used mechanically and it gives real time data but still due to mechanical instrumentation, it has more component dependency which leads it to be failure in cricket bowling action where the subject(bowler) moving very fast and due to burden of instrument the subject will not be able to concentrate on task. To overcome on this problem image processing is being used through computer languages which must be work with respect to requirement of ICC [3, 5]. Bone Mean detection method is a computerized method similar to Ferdinands’s Method [4] but with main significance of automatic detection.

Through extensive experiment results, we have observed that the difference of recorded angle between bone mean detection and elgon is nearly 0.2 which is negligible i.e. 5.83 and 5.80 respectively.

5. Conclusion

Through various trials we conclude that due to advance feature of being comfortably to subject (bowler) and automatic processing bone mean detection method is far better then elgon with restriction to use in net practice.

For excellent results both modes need high speedy camera such as above 200fps which is not been used in our case. The model can be enhanced by network based system so that we can monitor bowlers throughout the world.


  • Susan J. Hall, “Basic Biomechanics” ,3rd edition, 1999
  • England and Wales Cricket Board - Cricket Coaches Manual. National Cricket Coach Initiative, 2000.
  • The laws of cricket. http://www.cricinfo.com/db/societies/eng/acs/cricket_history/laws/index.html
  • E. D. Ferdinands, and U. G.Kersting, “The Biomechanics of Illegal Bowling Actions in Cricket”, University of Auckland, 2004 (unpublished).
  • ICC , “Regulations for the review of bowlers reported with suspected illegal bowling actions”, July 2006.
  • Adobe Premiere version 6.0, http://www.adobe.com/products/premiere
  • Matlab version 7.3 R2006b, http://www.mathworks.com

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