Which Extrinsic and Intrinsic Factors are Associated with Non-Contact Injuries in Adult Cricket Fast Bowlers?

BACKGROUND: The high prevalence of injury amongst cricket fast bowlers exposes a great need for research into the risk factors associated with injury. Both extrinsic (environment-related) and intrinsic (person-related) risk factors are likely to be implicated within the high prevalence of non-contact injury amongst fast bowlers in cricket. Identifying and defining the relative importance of these risk factors is necessary in order to optimize injury prevention efforts. OBJECTIVE: The objective of this review was to assess and summarize the scientific literature related to the extrinsic and intrinsic factors associated with non-contact injury inherent to adult cricket fast bowlers. METHOD: A systematic review was performed in compliance with the PRISMA guidelines. This review considered both experimental and epidemiological study designs. Studies that included male cricket fast bowlers aged 18 years or above, from all levels of play, evaluating the association between extrinsic/intrinsic factors and injury in fast bowlers were considered for inclusion. The three-step search strategy aimed at finding both published and unpublished studies from all languages. The searched databases included MEDLINE via PubMed, Cumulative Index to Nursing and Allied Health Literature (CINAHL), the Cochrane Controlled Trials Register in the Cochrane Library, Physiotherapy Evidence Database (PEDro), ProQuest 5000 International, ProQuest Health and Medical Complete, EBSCO MegaFile Premier, Science Direct, SPORTDiscus with Full Text and SCOPUS (prior to 28 April 2015). Initial keywords used were 'cricket', 'pace', 'fast', 'bowler', and 'injury'. Papers which fitted the inclusion criteria were assessed by two independent reviewers for methodological validity prior to inclusion in the review using standardized critical appraisal instruments from the Joanna Briggs Institute Meta Analysis of Statistics Assessment and Review Instrument (JBI-MAStARI). RESULTS: A total of 16 studies were determined to be suitable for inclusion in this systematic review. The mean critical appraisal score of the papers included in this study was 6.88 (SD 1.15) out of a maximum of 9. The following factors were found to be associated with injury: bowling shoulder internal rotation strength deficit, compromised dynamic balance and lumbar proprioception (joint position sense), the appearance of lumbar posterior element bone stress, degeneration of the lumbar disc on magnetic resonance imaging (MRI), and previous injury. Conflicting results were found for the association of quadratus lumborum (QL) muscle asymmetry with injury. Technique-related factors associated with injury included shoulder-pelvis flexion-extension angle, shoulder counter-rotation, knee angle, and the proportion of side-flexion during bowling. Bowling workload was the only extrinsic factor associated with injury in adult cricket fast bowlers. A high bowling workload (particularly if it represented a sudden upgrade from a lower workload) increased the subsequent risk to sustaining an injury 1, 3 or 4 weeks later. CONCLUSION: Identifying the factors associated with injury is a crucial step which should precede the development of, and research into, the effectiveness of injury prevention programs. Once identified, risk factors may be included in pre-participation screening tools and injury prevention programs, and may also be incorporated in future research projects. Overall, the current review highlights the clear lack of research on factors associated with non-contact injury, specifically in adult cricket fast bowlers. SYSTEMATIC REVIEW REGISTRATION NUMBER: Johanna Briggs Institute Database of Systematic Reviews and Implementation Reports 1387 (Olivier et al., JBI Database Syst Rev Implement Rep 13(1):3-13. doi: 10.11124/jbisrir-2015-1387 , 2015).

Extrinsic and intrinsic factors associated with non-contact injury in adult pace bowlers: a systematic review protocol.

REVIEW QUESTION/OBJECTIVE: Review question: which extrinsic and intrinsic factors are associated with non-contact injury in adult cricket pace bowlers?Review objective: the objective of this review is to determine the extrinsic and intrinsic factors associated with non-contact injury in adult pace bowlers. BACKGROUND: Cricket is generally considered to be a sport of low injury risk compared to other sports. In cricket, the pace bowler strives towards the adoption of a bowling technique with a relatively low injury threat that will, at the same time, allow for a fast (>120km/hr) and accurate delivery to the opposing batsman. However, of all the various roles of the cricket player, the pace bowler has the highest risk of injury, especially for low back and lower limb (lower quarter) injury. The reason for this high risk of injury is due to the inherent, high-load biomechanical nature of the pace bowling action. The high prevalence of injury amongst pace bowlers highlights the great need for research into factors associated with injury.Both extrinsic and intrinsic factors work in combination to predispose the bowler to injury. Extrinsic or environment-related factors include bowling workload (the numbers of overs a bowler bowls), player position (first, second or third change) and time of play (morning or afternoon). A high bowling workload has been linked with a higher risk of injury in pace bowlers. Foster et al. found in an observational study that bowling too many overs in a single spell or bowling too many spells may increase the pace bowler's risk of sustaining a low back injury. In another observational study, Dennis et al. found that an exceptionally high bowling workload as well as an uncommonly low bowling workload is associated with injury risk. The major extrinsic factors for bowling injury identified by Orchard et al. are a high number of match overs bowled in the previous week, number of days of play and bowling second (batting first) in a match. Extrinsic factors are known to make the bowler more susceptible to injury, especially in the presence of intrinsic factors.Intrinsic, or person-related, factors include muscle strength, flexibility, balance and biomechanics. Intrinsic, strength-related factors, such as shoulder depression, horizontal flexion strength for the preferred limb and quadriceps power in the non-preferred limb are also significantly related to back injuries in fast bowlers. Both upper limb and lower limb-related intrinsic factors are known to be associated with injury. A prospective study by Dennis et al. aimed to identify the risk factors for injury in adolescent cricket fast bowlers. Their findings concluded that bowlers with a hip internal rotation range of motion of ≤30° on the leg ipsilateral to the bowling arm were at a significantly reduced risk of injury compared with bowlers with >40° of rotation. Moreover, bowlers with ankle dorsiflexion lunge of 12.1-14.0 cm on the leg contralateral to the bowling arm were at a significantly increased risk of injury compared to bowlers with a lunge of >14 cm. Reduced hamstring flexibility was also associated with lumbar disc abnormalities. Bowling-related biomechanical risk factors for injury have been established such as trunk rotation of the shoulders by to a more side-on position during the delivery stride. Portus et al. also reported that shoulder counter-rotation was significantly higher in bowlers who reported lumbar spine stress fractures, while the non-trunk injured group displayed a more flexed knee at front foot contact and ball release. In addition to the above kinematic risk factors, there are high ground reaction forces associated with the power phase - between the front foot placement and ball release components of the pace bowling action. A combination of kinematic bowling related issues as described above and high ground reaction forces may predispose the bowler to injury.Morton et al. conducted a systematic review on pace bowlers between the ages of 13.7 and 22.5 years on risk factors and successful interventions for cricket-related low back pain. Young cricketers between the ages of 13 and 18 years are different to adults in terms of their physiology which impacts on their predisposition to injury and phases of healing. Young cricketers may differ from an adult population in that young pace bowlers who sustain injuries during their bowling career may have given up on the sport by the time they approach adulthood, and the composition of the adult pace bowler population group is therefore affected by natural selection which may cause this group to differ from the original population. Caution is thus advised when generalizing findings from this young population group to adult pace bowlers which emphasizes the need for studies amongst adult pace bowlers. Furthermore, the review by Morton et al. included articles that specifically investigated factors associated with low back pain. However, due to the interconnectedness between the spine and the lower limbs, kinematic variables affecting the spine will also affect the load placed on the lower limbs with subsequent risk of injury. The interdependent mechanical interactions in a linked segment system such as the system of motion of the low back can be caused by movement coordination patterns in other body segments. The systematic review by Morton et al. only included intrinsic factors while the proposed review will also look at extrinsic factors. Therefore, the primary objective of this review is to determine extrinsic and intrinsic factors associated with non-contact injury in adult pace bowlers.