The School of Human Movement and Exercise Science, University of Western Australia, Perth, last month examined for the third time the bowling action of Sri Lankan off-spinner Muthiah Muralitharan, now the world's highest wicket-taker in Tests.
The examination of Murali's newly unveiled 'doosra' delivery was conducted at the request of Sri Lanka Cricket and the International Cricket Council after he was reported by ICC match referee Chris Broad during the recent Test series against Australia in Sri Lanka for possible chucking.
rediff.com has gained access to the report submitted by the team that examined Muralitharan's action. After the report was submitted to Sri Lanka Cricket, the board and the ICC both advised Muralitharan not to bowl the 'doosra' for the time being.
For the benefit of our readers, we reproduce here the complete report:
Professor Bruce Elliott
Ms Jacque Alderson
Ms Siobhan Reid
Mr Daryl Foster (Cricket Authority)
IN response to a request from the Sri Lankan Cricket Board, directed through Mr Daryl Foster and the ICC (contact from Mr David Richardson) Mr Muttiah Muralitharan's spin bowling action was assessed in the Biomechanics Laboratory of the School of Human Movement and Exercise Science at the University of Western Australia. This request followed the match referee (Mr Chris Broad) lodging a "suspect bowling action report" on his "doosra" delivery during the recent Australian tour of Sri Lanka. Testing was therefore restricted to analysis of his "doosra" delivery.
Mr Muttiah Muralitharan arrived in Perth on 31st March 2004, and his initial testing took place on Thursday the 1st of April. This testing comprised:
* an anthropometric assessment of his bowling arm,
* a three-dimensional (3D) analysis of his bowling arm during the complete bowling action, although elbow angles are only reported from a position where the upper arm is horizontal to the ground until ball release (the area covered by the laws of the game). This involved filming Mr Muralitharan using a 12 camera opto-reflective Vicon system operating at 250Hz (fields per second).
The testing occurred in a laboratory environment, which permitted a full bowling run-up, such that a portion of the pitch was housed outside the laboratory. A laterally (side) placed video camera recorded his images during delivery to assist in the identification of ball release. A front-on video camera was used to assist in the selection of the best "doosra" deliveries. Mr Bruce Yardley, a former Australian spin bowler, who commented on the quality of each delivery, also assisted this task. He had been present in Sri Lanka during the recent Test series and could therefore comment on the quality of the laboratory compared with on-field bowling.
* His best six deliveries were then analysed. Those selected satisfied the criteria of breaking the appropriate way off the pitch and being bowled with appropriate intensity by the spin bowling expert.
The results from this testing session were verbally provided to Mr Muttiah Muralitharan and Mr Daryl Foster. In an attempt to ensure that all efforts were made to comply with ICC rules, Mr Muttiah Muralitharan, following consultation with the UWA biomechanics testing team, then underwent a period of 'technique remediation' with Mr Daryl Foster, a renowned cricket coach. A final 3D analysis, following ICC guidelines, was carried out on the 7th April. This report includes the results from both testing sessions. A preamble prior to the presentation of these data is included to assist with the interpretation of the results.
It is important when reading the following report that consideration is given to a number of issues. These include the accuracy of the measurement system used in bowling assessment (repeatability and validity of measures), range of acceptability of elbow angles in the critical region (from when the upper arm is parallel to the ground until ball release) and finally differences or similarities between fast and spin bowling actions.
Accuracy of measurement system
The opto-reflective 12 camera Vicon System that recorded at 250 pictures/sec has an error margin of approximately 1 degree in data collection. On-field recording systems, using a minimum of 3 high-speed video cameras for spin bowling, have accuracy levels of approximately 4 degrees, although these error margins were recorded in a laboratory environment (Richards, 1999).
The identification of elbow and shoulder joint centres in on-field data collection, where a shirt is worn, also involves large errors. In a match the ability to differentiate anatomical movements such as "elbow extension" by digitising segment end-points, particularly if you have segment rotations, is extremely difficult and prone to error. This is certainly the case with spin bowlers. It is therefore not surprising that laboratory testing is preferred, particularly for spin bowlers, where an appropriate pitch length and run-up can be structured. This is clearly the only way to test players, where data would be able to withstand scientific and therefore legal scrutiny.
Range of acceptability of elbow angles
The International Cricket Council (ICC) guidelines have been structured around fast bowling, so ranges of acceptability (10 degree fast bowling; 5 degree spin bowling) may, in fact, need to be modified for spin bowling. Portus et al (2003), the only published work in the area of changes of elbow angle during fast bowling, suggested the ICC range of acceptability should be increased to 15 degrees if a large number of current fast bowlers are not to be subject to scrutiny and then remediation (none has been called for "throwing"). The logic in reducing the margin for fast bowlers compared with spin bowlers is based on the lower speed delivery of this classification of bowler. However, while run-up speed and length of arm are generally higher for fast bowlers, spinners such as Muttiah Muralitharan actually have a similar rotational speed of the arm system. Mr Muralitharan recorded a similar time (= 0.08s), from arm horizontal to release, to that recorded by Shabbir Ahmed Khan, the Pakistan fast bowler recently tested by this team. Therefore a case can certainly be made for some spin bowlers such as Mr Muralitharan to have the same range of acceptability in elbow angle to that of fast bowlers.
2. ANTHROPOMETRIC ASSESSMENT
Mr Muttiah Muralitharan
|Wrist flexion-extension||78 deg flexion, 50 deg extension||Not applicable|
|Wrist abduction-adduction||26 deg abduction, 26 deg abduction||Not applicable|
|Forearm abduction angle ("carry angle")||18 deg||0 deg|
|Elbow flexion-extension||*Static 35 deg (flex) Dynamic 24 deg (fixed)||
0 deg (full extension)
|Shoulder internal rotation||68 deg||40 deg|
|Shoulder external rotation||
* The dynamic value is the smallest flexion angle recorded while bowling (i.e. under load)
The anthropometry assessment clearly shows that Mr Muralitharan has a natural 35 degrees of elbow flexion while standing, which during the delivery action (under load) reduces to a value of approximately 24 degrees. Therefore any biomechanical assessment of his bowling action must take this 24 degree angle into account. In practical terms this means that his elbow joint, depending on the load, will always display at least some flexion. His elbow abduction angle is also such that it displays a relatively large "carry angle".
Mr Muralitharan's shoulder external rotation range is higher than normal, which allows him a greater range of motion during delivery. While this is an advantage in the development of speed, it also is a natural occurrence and does not therefore fall outside the bounds of human normality nor the rules of cricket. While this may be an advantage in bowling, it does not directly impact on the extension of the elbow.
However, the external rotation at the shoulder, combined with the 18 degree "carry angle" and 24 degree of permanent elbow flexion (see dynamic flexion above) will give the impression of "preparation for a throw". This is particularly true when the action is viewed in two-dimensions (e.g. television, or when observed by an umpire from a fixed position).
3. INITIAL BOWLING ASSESSMENT
Mr Muralitharan attended the biomechanics laboratory at the School of Human Movement and Exercise Science on April 1st 2004. The results from this initial testing session are presented below.
Session 1 Results:
Following a warm-up, markers were attached to Mr Muralitharan as shown in Figure 1. The mean velocity of six deliveries selected for analysis was 64 km/hr. A mean elbow extension range of 14 degrees was recorded for these six "doosra" deliveries (Table1, Figure 2). The curves graphed in Figure 2 clearly show that each delivery was bowled with a similar action. One can then be confident that Mr Muralitharan bowls with a similar action in his "doosra" delivery. While one could argue that this extension is acceptable, it is outside the current extension threshold of 5 degrees set by the ICC. Hence a period of remediation followed aimed at reducing the level of elbow extension from upper-arm horizontal to release.
Figure 1: Defining elbow flexion-extension axis (not reproducible).
Table 1: Mean changes in elbow angle from upper arm horizontal to ball release (six deliveries)
|Delivery type||Range of Extension ( )||Speed (km/hr)|
|Doosra||14 deg (+ or - 2 deg) extension||65 (+ or - 3.0)|
4. BOWLING TECHNIQUE REMEDIATION
See attached Remediation Report. [below]
5. FINAL BOWLING ASSESSMENT
Following the period of remediation a second biomechanical analysis of Mr. Muralitharan's "doosra" delivery was conducted on the 7th April, 2004. The results from this testing session are presented below.
Session 2 Results:
The mean extension for the elbow from upper arm horizontal to ball release was 10.2 degrees (Table 2, Figure 3). Variations in the elbow extension curves (Figure 3) and the small standard deviation for the 6 deliveries (Table 2), show that each of these deliveries is very close to a 10-degree level. He therefore bowls with a consistent action.
His mean delivery speed of 72 km/hr, which is at the higher end of his "test match range" of 65-75 km/hr, shows that he was bowling with intensity in this laboratory environment. The spin bowling expert also testified to the fact that the deliveries analysed deviated in the appropriate manner with "venom". He rotated his upper arm from the horizontal to release in a mean time of 0.072s, which is quicker than in Test 1 and also quicker than the time taken to rotate through the same angle by Shabbir Ahmed Khan.
Table 2: Changes in elbow angle from upper arm horizontal to ball release
|Delivery type||Range of extension ( deg)||Speed (km/hr)||Match range (km/hr)|
|Doosra||10.2 deg (+or- 0.6 deg) extension||72 (+ or - 0.3)||65-75|
Following remediation Mr Muralitharan bowled with an increased flexion angle. However, the remediation had the effect of reducing elbow extension range from 14 degrees to 10 degrees. (See Figures 2 & 3)
In making recommendations regarding Mr Muralitharan the following should be stated. While a full run-up and standard pitch were used, data were collected in a laboratory environment. It is our considered opinion that this is the only way to record accurate and reliable 3D data of elbow movement, particularly for spin bowling. The key to the issue with reference to a spin bowler is the quality of the delivery and the rate of rotation of the upper arm. In our case Mr Muralitharan produced high-quality deliveries with an upper arm action that was similar in rotational speed to that of a fast bowler. The mean time for his upper arm to move from the horizontal to release in Testing session 2 (= 0.072s) was compared with the same movement recorded on video from the recent Sri Lanka vs Australia Test series. This video was provided by Mr Muralitharan. While the positioning of cameras for data from the Test series was not ideal and video images were recorded at a slower rate (50 fps), it was evident that the time for the upper arm to move from the horizontal to release was similar for the Test series and the laboratory testing. Mean ball velocity at testing session 2 of 72 km/hr was also at the upper end of the range commonly reported for Mr Muralitharan under Test conditions. We therefore contend that the bowling action recorded was similar to that used in a Test match.
A case may be made for Mr Muralitharan's initial elbow extension to be acceptable at 14 degrees. Particularly when one considers the speed of his arm rotation is similar to that of a fast bowler and the only scientific data related to fast bowling suggested an increase in the acceptable extension threshold from 10 degrees to 15 degrees (Portus et al, 2003). However, the mean extension across 6 deliveries was outside current ICC guidelines for fast bowlers.
For this reason a period of technique modification was carried out to reduce the level of elbow movement during the delivery of his "doosra". Following this remediation his level of elbow extension reduced to 10 degrees, which is within fast bowling guidelines. We contend that because the speed of his upper arm rotation is as fast and in some cases quicker than fast bowlers, his level of acceptability for elbow extension should also be set at the 10 degree mark. With no spin bowling data base to make a comparison, this would seem both a wise and prudent recommendation. Following the findings from Portus et al (2003) we would also recommend that the ICC consider increasing the fast bowling extension threshold to 15 degrees.
Finally it is our considered opinion that Mr Muralitharan be permitted to continue bowling his "doosra" at least until a valid database is collected on the various spin bowling disciplines. The relatively minor level of elbow extension following remediation over the period from arm horizontal to release is not believed to give Mr Muralitharan an unfair advantage over batsmen or other bowlers.
Professor Bruce Elliott Ms Jacque Alderson
Portus, M, Mason, B, Rath, D & Rosemond, C (2003). Fast bowling arm actions and the illegal delivery law in men's high performance cricket matches. Science and Medicine in Cricket. R Stretch, T Noakes & C Vaughan (Eds), Com Press, Port Elizabeth, South Africa: 41-54.
Richards, J (1999). The measurement of human motion. A comparison of commercially available systems. Human Movement Science, 18: 589-602.
Daryl H Foster
Mr Muttiah Muralitharan (Murali) was cited by Match Referee, Mr Chris Broad, at the conclusion of the recent Test series, Sri Lanka versus Australia. The report indicated that an investigation should be carried out into a particular delivery termed the "doosra", which means the "other one" or the "one that goes the other way".
The Sri Lankan Cricket Board (BCCSL) requested me to arrange for a full biomechanical assessment of Murali's "doosra". This was to be undertaken in the Biomechanics Laboratory at the University of Western Australia. It should be noted that Murali did not bring with him any master tape supplied by the ICC. This is a requirement under points 2.1, 2.2 and 4.2 of the ICC Standard Analysis Protocol. However, Murali did bring with him some videotape from his own personal collection, showing him bowling his "doosra" in the recent Australia-Sri Lanka Test series.
INITIAL BOWLING ASSESSMENT
Murali was first subjected to an Anthropometric assessment, which confirmed previous results of Murali having a permanently flexed bowling arm with an excessive carry angle, but also with greater than normal shoulder and wrist flexibility. Murali then bowled in the Biomechanics Laboratory under simulated match conditions.
Mr Bruce Yardley was in attendance to validate that the deliveries Murali was bowling were in fact "doosras", and were delivered with the same technique as he had witnessed in the recent Test Series. Mr Yardley, a former great off-spin bowler, was a television commentator at the recent three Test match series, Sri Lanka versus Australia.
This initial test indicated Murali straightened his arm by an average measure of 14 degrees. This is 9 degrees over the ICC Tolerance Level for spin bowlers, which is currently 5 degrees.
After reviewing the results with the University of Western Australia Biomechanics group and Murali, it was decided to conduct another test the following day (2nd April) to ascertain if changes to bowling technique in anyway modified elbow angle during delivery. It was apparent that Murali bowled the "doosra" from wide of the crease and with an "open" action. It was decided that if he could get more "side-on" and deliver the "doosra" closer to the stumps, that this could reduce the amount of straightening of the arm i.e. between the horizontal arm position and ball release.
This test on 2nd April looked at only a few deliveries to ascertain if the result warranted a remedial programme being put in place. The results obtained showed a positive shift which indicated a 5 day remedial programme might make a significant difference. A re-test date was set for 7th April.
MURALI'S TECHNICAL PROBLEM
Murali began his run-up at too much of an angle to the bowling crease. This resulted in Murali bowling wide on the crease, which caused his bowling action to be quite open. Due to his permanent elbow flexion and carry angle, Murali does require a more horizontal rotation to allow his bowling arm to rotate efficiently. Therefore he will never be able to be completely side-on. Murali was unaware he had drifted into this open bowling position, which had occurred over a period of time. Murali felt that this more closed approach and vertical arm rotation would aid his effectiveness and he was enthusiastic about making the change.
Murali's "doosra" is an extension of his top-spinner where the back of his bowling hand faces the batsman just prior to delivery. I would suggest that Murali's greater than normal shoulder and wrist flexibility greatly improves the success of this delivery.
For the next five days Murali bowled in the nets twice a day to implement these changes to his technique. Throughout my coaching career at first class level, I have not come across a bowler, with the possible exception of Lillee, who knows his body and his technique better than Murali. He was able to adjust to the technical changes quite easily, as he maintained he used to bowl with this technique earlier in his career. Changes made include:
* Reduced angle of run-up with approach now much straighter.
* Delivery from much closer to the stumps.
* Technique to become more side-on with back foot close to parallel to the crease, hips and shoulders facing the stumps and looking behind the front arm.
* Alignment of the feet in the delivery stride to become more angled towards the onside.
It was envisaged these changes should enable Murali's bowling arm to arrive at the horizontal position, having traversed a more vertical plane. The result would be to reduce the amount of overall extension of his bowling arm between the horizontal position and ball release.
Murali was re-tested on Wednesday, 7th April, at 5.30 pm. This test conformed to all ICC protocols. The result revealed a significant improvement, with the amount of elbow straightening of the "doosra" delivery reduced from 14 degrees, which was recorded in the initial test, to 10 degrees in the re-test. Allowing for this substantial improvement, Murali is still 5 degrees in excess of the ICC Tolerance Limit for spin bowlers. The protocol of "test remediate re-test", also used with Shabbir Ahmed, has again produced an improved result. In both the initial and post-test, Murali bowled with an upper arm rotational speed which corresponds to television coverage of his doosra delivery.
REVIEW: Coach's Perspective
Murali is now bowling the "doosra" with a more side-on action, which has reduced the amount of straightening of his bowling arm between horizontal and ball release to 10 degrees.
Ten degrees of straightening bowling the "doosra" is still 5 degrees above the tolerance limit set by the ICC for spin bowlers. However, the following should be taken into consideration.
ICC tolerance figures of 10 degrees, 7.5 degrees and 5 degrees for bowlers ranging from fast to spin are based on what information, studies or research?
Without knowing what the situation is with other spin bowlers, it would seem unrealistic to ban Murali's "doosra" without the benefit of proper research having been undertaken into "normal" spin bowlers.
Other off-spin bowlers, in particular Harbhajan, Saqlain and Shoaib Malik, all bowl the doosra delivery, which suggests for comparison purposes their "other one" should also be analysed.
Murali's arm velocity from horizontal to ball release is very similar to that of Shabbir Ahmed's, a fast bowler recently tested at the University of Western Australia. This raises the question of why 10 degrees of extension for a fast bowler is acceptable, with only 5 degrees of tolerance granted to a spin bowler whose arm speed is similar.
The question also has to be posed as to when does a bowler gain an advantage from "straightening". Marc Portus, in his latest research into fast bowling, suggests 15 degrees as being a point after which there may be some speed advantage gained by the fast bowler. However, no such research has been conducted into spin bowling. It may be that 15 degrees of extension be allowed to all types of bowlers no matter what speed they bowl at, beyond which it be termed an illegal delivery.
Marc Portus's fast bowling research investigated thirty-four deliveries bowled by twenty-one fast bowlers. Fourteen of these deliveries were in excess of the ICC Tolerance Level of 10 degrees. When the tolerance level was raised to 15 degrees there were still four illegal deliveries. This indicates there are fast bowlers who are regularly operating outside legal limits, whereas Murali only bowls his "doosra" approximately one in every twelve deliveries.
It is possible that the straightening of the elbow by all types of bowlers is a biomechanical reality. It is my contention that since fast bowlers have been operating with a front-on action, they have regularly extended their elbow more than the accepted limit, particularly when they bowl short-pitched deliveries.
The analysis of Murali's "doosra" conducted at the University of Western Australia's Department of Human Movement and Exercise Science used the most up-to-date technology and highly trained staff to determine the degrees of straightening of his bowling arm.
This process needs to be used earlier in a bowler's development so as to provide a factual base for future discussion of the laws pertaining to legitimate bowling actions.
In conclusion Murali, who has been tested more than any other bowler in the history of the game 1995, 1999, and now 2004, possesses different physical characteristics which make him a unique bowler.
The results from these tests suggest that a straightening of 10 degrees when he bowls his doosra is not excessive and that should not therefore be deemed advantageous.
Daryl Foster OAM