Assessing the merit of shoulder counter-rotation as a risk factor for lumbar bone stress injuries: a systematic review

Introduction: Recently published data by Cricket Australia shows the high incidence of lumbar bone stress injuries (LBSIs) in young fast bowlers. Shoulder counter-rotation (SCR) may be described as the rotation of the shoulders to a more side-on position after back-foot contact. SCR has been variedly posited to be either a constituent of, or the defining principle of, a mixed-action; the definition of which has also varied greatly. Despite this, literature has implicated increased SCR in LBSI risk, prompting an emphasis on coaching a reduction in SCR. A systematic review is therefore warranted to assess the merit of SCR as an LBSI risk factor in fast bowlers. Methods: Embase, Medline, PubMed, Scopus and Web of Science databases were searched (March 2023). Search terms related to cricket bowling, injury, the lumbar spine, and SCR. Strict inclusion criteria focused on published fast bowling original studies, with clearly defined statistical assessment of the association between SCR and LBSIs. Other factors discussed in included studies said to be directly related to LBSIs were considered if this was statistically assessed in relation to SCR. Studies were excluded if not clearly LBSI-specific (for example, lower-back pain). Quality assessment used a bespoke scale to maximise relevance, based on systematic reviews examining cricket non-contact injuries (10 questions, scorable as zero, half or one point). Results: Ten studies passed the inclusion criteria. The average quality assessment score was 6.25 out of 10. Discussion on generalisability of results was often inadequate. No studies accounted for confounding factors that may affect SCR findings, while only half provided limited discussion on such factors. SCR values greater than 30° or 40° have been suggested to be linked to LBSIs, with these values differing across studies. Only five studies directly implicated SCR as an LBSI risk factor, while four more-recent studies found no association. The other correlated SCR with increased lumbar loads, although this was described as un-noteworthy. Discussion: A limitation to the literature is the varied definitions used to define SCR and mixed-actions. In some instances, this raises validity concerns and care should be taken not to use the two terms interchangeably. Importantly, technical factors in other stages of the action that may affect results are rarely discussed, if at all identified. This review highlights conflicting findings regarding the association between SCR and LBSIs, varied operational definitions, arbitrary and varied SCR thresholds, few efforts to control for confounding factors, and lack of causality. It is worth noting some excluded reports had associated SCR with LBSIs with no statistical analysis, rather the authors had only suggested this association. This serves to further weaken the evidence-base for SCR as a risk factor. Impact/Application to the field: SCR is cited in coach education and its reduction is a focus of coaching practice. However, given the limitations of the literature, serious doubt must be raised about the focus in coaching on reducing SCR to limit LBSI risk in young fast bowlers. Coaches should be aware of these limitations before implementing a coaching strategy. Declaration: My co-authors and I acknowledge that we have no conflict of interest of relevance to the submission of this abstract.