The world’s top-two ranked bowlers aren’t competing at the Cricket World Cup, which began last weekend in Australia and New Zealand. But they’re not sidelined because of injuries. When they do return to play, it will be thanks to motion-capture technology and biomechanics algorithms. And improvements to those technologies could mean a much faster return to play for other bowlers.
Pakistan’s Saeed Ajmal has spent the past four months remodeling his bowling technique after the International Cricket Council (ICC) suspended him for bowling with an illegal action known as “throwing.” Last Sunday, the ICC cleared Ajmal, but it was too late for him to make the Pakistani squad, which had been chosen several weeks ago.
West Indian Sunil Narine made himself unavailable for the World Cup after he picked up a one-game ban for having a suspect bowling action. Narine’s ban came during an unofficial tournament last October. Fearing that he’d be banned by the ICC if he continued playing, Narine, too, has been working on his technique with specialist coaches and analysts.
Bowling is a peculiar action for those new to cricket. The game’s rule makers have never allowed bowling with an arm that starts off bent and ends up straight. Such an action would give the ball too much speed and too much spin and give the bowler an unfair advantage, they’d always said.
That was until studies in the 1990s and early 2000s showed that it was physically impossible to bowl without some degree of arm flexion and extension. In 2003, the ICC decided to permit 15 degrees, but no more. Last year, Ajmal tested at 40 degrees. During 2014, the ICC suspended six other international bowlers for throwing—more bans than in the previous 15 years combined.
The ICC advises international umpires to report any bowler who looks as if he or she (the same rules apply for women’s cricket) might be exceeding the limit. But the naked eye can’t discern precisely if someone is breaking the rules, so bowlers must have their actions checked at one of the ICC’s four testing centers—high-tech performance-analysis units at Cricket Australia’s National Cricket Centre, in Brisbane, Australia; Sri Ramachandra University, in Chennai, India; Loughborough University, in England; and Cardiff Metropolitan University, in Wales.
The technology allows “the testers to locate the wrist, elbow, and shoulder joints to determine the elbow extension,” says ICC spokesman Sami Ul Hasan. In the typical analysis, bowlers goes through their repertoire of deliveries, and the markers reflect light, which the analysts track with motion-capture cameras, high-speed infrared cameras, and radar guns. From the collected data, the system estimates the positions, in three dimensions, of the joints and limbs as the bowler lets go of the ball.
Getting bowlers to a center, testing them, evaluating the results, and writing up the report can take three weeks. The ICC has promised to reduce this to seven days for the duration of the World Cup. Players can’t resume their careers until they’re cleared.
This is all new to cricket, however, and there are some problems. Opinion is divided as to whether to put markers on joints or soft tissue to get the most accurate reading, for instance. And analysts can’t put golf-ball-size markers on bowlers’ bodies during matches. They can monitor only what players do in the lab.
The ICC is currently looking into wireless wearable inertial sensors. Inside a sleeve, accelerometers and gyroscopes would continuously stream data to a nearby computer. “Testers place an accelerometer and a gyroscope at the elbow, wrist, and shoulder,” explains Saad Qaisar from the School of Electrical Engineering and Computer Science at the National University of Sciences and Technology, in Islamabad, Pakistan, who has done his own research into wearable inertial sensors for cricket. “The gyroscope provides angular rotation of the body part with reference axis; the accelerometer provides the acceleration and velocity data. From this you can calculate the arm angle during the bowling arc and detect the all-important moment the ball is released.”
Qaisar’s work is still at the developmental stage, however, and the ICC’s inertial sensors aren’t ready either. For one thing, if the sensors move on the bowler’s arm, the system’s calibration is affected, which corrupts the data.
Steve Haake, director of the Centre for Sports Engineering Research at Sheffield Hallam University, says that bowlers wearing sensor systems will still know they’re being tested and might change what they’re doing for the duration of the test and go back to the previous, illegal technique afterward. “The sleeve might also feel a bit tight or weird and inadvertently affect how someone bowls,” he says.
According to Paul Glazier, an independent sports and human movement consultant, it would take markerless motion capture to test bowlers’ actions in a game without them knowing.
Filmmakers and computer-game designers use markerless motion capture to record the movements of actors playing animated characters. A computer algorithm analyzes multiple streams of optical inputs, identifies human forms, and breaks down the data for tracking purposes.
But systems designed for film aren’t accurate enough, says Haake. “They are more interested in image quality and don’t care what the answer is to the nearest degree, as long as things look about right. We need an algorithm that allows us to process the data to the level of accuracy needed,” he says.
About the Author
Crispin Andrews is a freelance writer from England who covers science, technology, popular culture, history, and most importantly, cricket. His review of the Alan Turing biopic The Imitation Game appeared in the December 2014 issue of IEEE Spectrum.