High acute:chronic workloads are associated with injury in England & Wales Cricket Board Development Programme fast bowlers

Objectives The objectives of this study were to explore the relationship between acute (1 week) and chronic (4-week average) bowling workloads and injury risk in National Development Programme fast bowlers, and to investigate individual differences in the relationship between acute:chronic workloads and injury. Design Prospective cohort study. Methods Bowling workloads and injury data were collected prospectively for 29 male fast bowlers (age range 15–18) on a National Programme over two years. Workload variables were calculated and the likelihood of injury and individual effects were explored using a generalised linear mixed effects model and magnitude-based inferences. Results Acute:chronic workloads of 109–142% (relative risk [RR]: 1.46, 90% CI: 0.93–2.29; likely harmful), and ≥142% (RR: 1.66, 90% CI: 1.06–2.59, likely harmful) were associated with a substantial increase in injury risk compared with the reference quartile (<87%). A high chronic workload (>83 balls) substantially attenuated the influence of a high (>108%) acute:chronic workload ratio on injury risk (RR: 0.35, 90% CI: 0.17–0.74). Significant individual differences in the acute:chronic workload-injury relationship were evident. Conclusions The present study provides further evidence of the association between 'spikes’ in workload and injury risk, but also demonstrates that this relationship is individual-specific and dependent on the level of chronic workload. Support teams for fast bowlers should monitor bowling workloads to avoid rapid fluctuations but should also base decisions on individualised data.