Exercise-based injury prevention for community-level adolescent pace bowlers

Sporting injuries are on the rise and wide-scale injury prevention strategies are needed in community-level sport. Research indicates that community-level adolescent pace bowlers could benefit from exercise-based injury prevention programs (IPPs), however, a specific program for this group has not been developed. The primary aim of this thesis was to therefore develop a specific IPP for community-level adolescent pace bowlers and investigate if this program could modify risk factors for injury in this population. The Translating Research into Injury Prevention Practice (TRIPP) framework guided the progression of studies in this thesis. In Chapter 2, risk factors for injury in adolescent pace bowlers were systematically reviewed. The review included all experimental and observational studies that reported risk factors for non-contact injuries in pace bowlers aged 12-19 years. The Newcastle-Ottawa Quality Assessment Scale was used to assess risk of bias. In Chapter 3 the various barriers and facilitators to program implementation at the community-level were identified and used to guide the development of an IPP that was appropriate for community-level adolescent pace bowlers. In Chapters 4 and 5 a cluster-randomised controlled trial was employed to examine the efficacy of this IPP to modify neuromuscular risk factors and alter bowling kinematics. Eligible pace bowlers from eight cricket organisations (clusters) were recruited and then randomised into either an intervention group or control group. The intervention group completed an eight-week IPP while the control continued their normal cricket activity. Either side of the eight-week intervention period all participants attend a baseline and follow-up session where measures of muscle strength, muscle endurance, dynamic neuromuscular control and bowling kinematics were assessed. The treatment effect of the IPP was estimated with linear mixed models. Chapter 2 identified several potentially modifiable risk factors for injury in adolescent pace bowlers and these included; excessive lateral trunk flexion while bowling, kinematics of pelvis and hip while bowling, reduced trunk endurance, and poor lumbo-pelvic-hip movement control. There were conflicting results amongst the studies which investigated the mixed technique, bowling workload, and quadratus lumborum asymmetry. Among the five cross-sectional studies, risk of bias was high and very high. Of the 11 cohort studies, three were rated as low risk of bias and eight as high risk of bias. With the information gathered in Chapter 2, an exercise program to modify risk factors was developed in Chapter 3. The program included exercises to improve; eccentric strength of the external shoulder rotators, hip adductor strength, eccentric hamstring strength, dynamic neuromuscular control of the lumbo-pelvic region and lower-limbs, and trunk extensor endurance. Chapter 3 also considered the various facilitators to program implementation at the community-level, and therefore included exercises that were; simple to learn, non-reliant on expensive equipment, and time-efficient. In Chapter 4 the efficacy of this newly developed IPP to modify neuromuscular risk factors was assessed. There were significant treatment effects (estimated marginal mean with 95% confidence intervals) favouring the intervention group for; isokinetic shoulder strength (90°/s) (0.05 Newton meters per kilogram (N.m/kg); 0.02 to 0.09), isokinetic hamstring strength (60°/s) (0.32 N.m/kg; 0.13 to 0.50), hip adductor strength dominant side (0.40 N.m/kg; 0.26 to 0.55) and non-dominant side (0.33 N.m/kg; 0.20 to 0.47), Star Excursion Balance Test reach distance dominant side (3.80 percent of leg length (%LL); 1.63 to 6.04) and non-dominant side (3.60 %LL; 1.43 to 5.78), and back endurance (20.4 seconds; 4.80 to 36.0). No differences were observed for isokinetic shoulder strength (180°/s) (p=0.09), isokinetic hamstring strength (180°/s) (p=0.07), lumbo-pelvic stability (p=0.90), and single leg squat knee valgus angle (dominant p=0.06, non-dominant p=0.15). In Chapter 5 there were significant treatment effects favouring the intervention group for shoulder counter-rotation (-3.75°; -7.19 to -0.32) and lateral trunk flexion relative to pelvis (-2.24°; -3.97 to -0.52). There were however, no significant between-group differences for; global angles of lateral trunk flexion at front foot contact (FFC) (1.2°; -2.5 to 4.8), global angles of lateral trunk flexion ball release (BR) (-0.5°; -3.0 to 2.0), pelvis rotation FFC (0.9°; -4.0 to 2.2), pelvis rotation BR (-1.1°; -5.7 to 3.6), front hip angle FFC (1.6°; -3.6 to 6.7), front hip angle BR (-1.6°; -5.0 to 1.9), front knee angle FFC (-1.1°; -4.5 to 2.3), front knee angle BR (1.7°; -5.6 to 9.1), or ball velocity (1.1 km/h; -7.5 to 9.7). This thesis demonstrates that the TRIPP framework can used to successfully guide the process of injury prevention in community-level adolescent pace bowlers. The IPP in this thesis was also able to modify several neuromuscular and biomechanical risk factors, however a number of measures were not altered. Future research is needed to refine the current IPP and investigate if it can reduce injury risk in a real-world setting.