Kinetics at front foot contact of cricket bowling during a 10-over bowling spell
The purpose of this study was to determine what effect bowling a 10 over spell (60 balls) would have on approach velocity, vertical ground reaction forces and shock attenuation during the front foot contact of a delivery stride in cricket.
Ten Amateur cricket players (age 27±4 years, height 1.78±0.3 m, mass 80.6±8.5 kg) participated in the study. Testing was conducted at University of Nevada, Las Vegas in the Biomechanics laboratory. Participants performed a 10-over bowling spell from a 12 meter run-up. These dependent variables were measured and calculated during the bowling protocol: (1) approach velocity (2) vertical ground reaction force (vGRF) and (3) shock attenuation (SA). A 15 min self-directed warm-up was performed prior to starting the 10-over bowling spell. After the warm-up was completed subjects were instrumented with two uni-axial accelerometers (PCB Piezotronics, model #352C68-6 and #352C68) to obtain acceleration data (1000Hz) and ultimately calculating shock attenuation. One accelerometer was placed on the distal anterior-medial aspect of the tibia and the second accelerometer was placed on the forehead along the midline of the body. Participants were then asked to bowl a 10 over bowling spell with 8 min breaks between. During the delivery stride participants had to strike the force platform with their front foot. Accelerometer and vertical ground reaction force data were collected for the time total time that the front foot was in contact with the ground. A force platform (Kistler, 9281C, SN-616902) was used to collect vertical ground reaction force data (1000Hz).
Dependent variables namely approach velocity, vertical ground reaction force and shock attenuation was analyzed using one way repeated measures ANOVAs with planned comparison tests to determine where differences occurred across the 10 overs. Overs were combined into beginning (overs 1&2), middle (overs 5&6) and end (overs 9&10). SA was calculated by the following equation: SA = (1- Head/Leg)*100.
A significant change across the 10-over bowling spell were found for approach velocity (p<0.001), vertical ground reaction force (p<0.024) and shock attenuation (p<0.032). Planned comparison tests identified a significant difference (p<0.05) for APV between the beginning (4.34 ± 1.22 m/s) and middle (5.18 ± 1.42 m/s) as well as a significant difference between middle (5.18 ± 1.42) and end (4.13 ± 1.27 m/s). The vGRF results illustrated a significant difference (p<0.05) between the middle (4.09 ± 0.81 BW) and the end (3.76 ± 0.58 BW). No significant difference (p<0.05) was found in vGRF between the beginning (4.03 ± 0.69) and the middle (4.09 ± 0.81BW). An overall significant difference was found in SA across all 10 overs. A significant difference was found between the middle (79.48 ± 10.43%) and the end (78.23 ± 10.72%) as well as between beginning and end.
High vGRF values have has been reported in front foot contact during cricket bowling in fast/medium bowlers which might play a role in overuse injuries experienced by bowlers. This study provided groundwork in understanding how these forces change over a 10-over bowling spell and how these forces maybe attenuated during front foot contact. It was concluded that there was a definite change observed across the 10 overs in the magnitude of vGRF produced and how these forces are attenuated. This study suggests that coaches and fitness specialists should pay careful attention to these changes relative to overuse injuries potential.