Fast bowlers a 'shoe-in' for injuries

Fast bowlers a 'shoe-in' for injuries
A team from the University of South Australia will present their research on the biomechanical effects of three cricket shoes commonly used by fast bowlers to the Australasian Podiatry Conference today in Melbourne.
Lead researcher, masters student Chris Bishop from the Sansom Institute for Health Research, says the huge forces that a fast bowler's legs and lower body are subjected to can create injury.
"During bowling three different forces act at the front and back foot and the magnitude of these differ between the feet," he said.
"The largest forces are the vertical forces which are attenuated directly up the leg and they can be anything from five to nine times the individual's body weight, so they really are quite large forces.
"The braking forces can be in the vicinity of two to four times body weight."
Mr Bishop, who is a consultant podiatrist to the South Australian Cricket Association, says the forces are largest as the front foot hits the ground.
"There's a high force on the front leg on initial contact. That force has to be absorbed somewhere by the natural shock absorbers [of the lower limb], that might be through ankle joint motion or knee joint flexion," he said.
Stress fractures of the tibia are another common injury, says Dr Dominic Thewlis, who is a co-author of the research, which is being prepared for submission to a peer-reviewed journal.
"[What happens] when you load a bone repeatedly with a very high load, which these fast bowlers do during periods of activity and particularly in Test match cricket, is that it doesn't actually give the bone sufficient opportunity to recover properly," he said.
Shoe comparisons
For the study,customize osiris shoes, the authors compared two models of top-selling cricket shoes against custom modified shoes.
The modified shoes that fast bowlers wear are often a running shoe or cross-trainer with a stiff, spiked sole on the top of the existing outsole.
Mr Bishop says bowlers modify shoes in this way partly for fashion reasons and partly because of perceived comfort and performance advantages.
"These shoes have been made specifically for the demands of cricket and when you modify a normal cross trainer you're actually changing the structural properties of the shoe," he said.
By changing the characteristics of the shoe, the researchers found some evidence athletes are reducing the shock absorption ability of the foot, transferring shock up through the knee, the hip, to the lower back.
In the course of testing shoes at the Australian Institute of Sport, four fast bowlers bowled three overs each, wearing a different pair of shoes for each set of six balls.
The bowlers' techniques and the forces involved were examined using a system of 20 cameras and force platforms to measure both front leg and back leg heel strike.
"The main thing we're seeing in our results is the effect of footwear on the front knee," Mr Bishop said.
"We're seeing that the custom modified shoe seems to be increasing that external rotation moment, which we think could be a mechanism of injury.
"Whether that's a predictor of injuries in cricket is yet to be determined, but it's certainly provided an additional insight into a mechanism of injury that needs to be investigated further.
"We have to be careful with the data that we have because it's a very small sample size but the custom modification may actually be hindering the performance of the shoes.
"But we have some preliminary data to show that this process may cause changes that could lead to injury."

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