Three-dimensional lumbar segment kinetics of fast bowling in cricket.

Cricket fast bowlers have a high incidence of serious lumbar injuries, such as lesions in the pars interarticularis. Kinematic studies have shown that bowling actions with large shoulder counter-rotation are associated with significantly higher incidences of lumbar injury. However, in bowling, there has been no calculation of the spinal loads, which are the causal mechanisms of such injuries. In this study, 21 fast bowlers (22.4+/-3.9 years) of premier grade level and above were tested using a three-dimensional (3D) motion analysis system. The mean ball release speed was 31.9+/-2.8 m s(-1) and ranged from 27.0 to 35.6 m s(-1). Kinematics and kinetics were calculated for lumbar spine lateral bending, rotation, and flexion during the delivery and power phases of bowling. Power calculations were used to define the actuation of lumbar spine motion as either active or controlled. The actuation of the lumbar spine was complex, involving multiple sequences of active and controlled motion. In addition, lumbar spine loads were largest during the power phase when the ground reaction forces were highest. In conclusion, the dynamic loads and the cyclical nature of their application when the spine is positioned near its end range of motion may be significant factors of injury to this region. In addition, the lumbar spine in bowling has to vigorously flex, laterally bend and rotate simultaneously in a complex interdependent sequence of actuation patterns. Therefore, any technical change to reduce injury susceptibility needs to consider the mechanics of whole body coordination and timing.