Tuesday, April 28, 2009

Cricket Bowling: Video Analysis of a Throwing Action

On the Video Analysis of Sports we are excited to show how video can be used to improve your performance in almost any sport. We are also interested when video or motion capture is used to study the intricacies of laws in sports.

This week Dudley came across an article about the use of a motion capture system to study the bowling action of a cricketer, http://www.gulfnews.com/sport/Cricket/10308342.html . For many years there has been controversy over legal bowling actions and numerous players have been called for suspect bowling. In fact the leading wicket taker in world cricket, Muttiah Muralitharan, was regularly called for a suspect action, early in his career. With the performance of 3D motion capture studies at the University of Western Australia, his action was finally ratified and was no longer called into question.

For those of you who know very little about cricket, here is a link with a brief explanation http://uk.cricinfo.com/link_to_database/ABOUT_CRICKET/EXPLANATION/ .
Bowling is the action of pitching the ball at the wicket (see link above) in an attempt to beat the batter.

There is a law in international cricket that the angle of the bowling arm (arm with the ball) cannot straighten more than 15 degrees during the final part of the bowling motion before releasing the ball. If it does then this motion can be considered illegal and in the end can result in a player being suspended from International cricket until he corrects his action.

It therefore makes perfect sense that video analysis is used to evaluate a cricket bowler's action before they are suspended. In fact the maximum change in angle was increased to 15 degrees based on a study using 3D motion capture analysis. Motion capture and biomechanical tests proved that it is almost impossible to bowl the ball without some flex or bending at the elbow and in 2004, it was discovered that many bowlers in International cricket flex their elbow more than the previously set limit during their bowling motion.

With video analysis we can:

  1. Capture the motion with high speed cameras, so we can assess the motion frame-by-frame and concentrate on the part of the bowling action that is relevant.
  2. Set up our cameras appropriately so we get a good view of the arm and how and where it bends.
  3. Measure the change in angle of the arm using mathematical concepts rather than "eyeballing" it.
  4. Capture the bowling action using multiple cameras to obtain a 3D view of the action and find the physical change in elbow angle rather than a 2D simple angle assessment.

The International Cricket Council (ICC) actually appoints a panel of human movement specialists to assess any possibly illegal bowling actions. This panel is instructed to use video and motion capture to analyze a suspect player's bowling and present their findings to a review board.

Here is a video of Muttiah Muralitharan bowling and taking the last few wickets on his way to the world record. His once suspect bowling delivery called the "doosra" is the first delivery you will see. In full speed and with the naked eye, it certainly looks like he is throwing the ball (straightening his arm by more than 10 degrees), but further investigation using 3D motion capture proved that this was not the case.

It is commendable that the ICC uses motion capture and technology to evaluate a rule that could cost a player his career. There are not many sports in which the player's action can be called into question; but all sports can benefit from some form of video analysis to improve players' performances.

If you have some sports video or are interested in analysis of a particular sport, let us know with a comment or send us an email.

1 comment:

Blogger said...

Great analysis of Cricket Bowling.

More Recommendations