Assessing the impact of hydrodynamic loads on shoulder joint injuries in swimming

Healthcare was identified as one of six key areas requiring additional research and innovation in the UK government's Industrial Strategy. Increasing activity and fitness levels across the general population is key to combatting the health challenges associated with obesity and an ageing population. Swimming is considered to be beneficial as it offers a non weight-bearing, full-body form of cardiovascular exercise widely available to the general public. Benefits to health and fitness might be offset, however, by an increased risk of shoulder injury, a common occurrence within the sport. The upper limbs produce a large proportion of the propulsive forces for swimming, suggesting that mechanical overload of the respective musculoskeletal structures might be related to the increased injury risk. However, little is known about the unsteady hydrodynamic forces acting on the arm or the mechanical loads in the upper limbs and their role in predisposing a swimmer to injury. This project aims to determine the fluid forces acting on a swimmer's arm and elucidate mechanisms of shoulder injury by understanding how this load is shared between the musculoskeletal structures around the shoulder joint.
Computational models allow the internal loading conditions to be quantified provided that the musculoskeletal anatomy, kinematics and external forces are known. The external, hydrodynamic forces acting on a swimmer are governed by the limb geometry and the local flow velocity defined by the stroke path. These unsteady forces cannot be measured and have to be derived from computer simulations, informed by detailed stroke kinematics and the local arm geometry. An immersed boundary CFD method will be used to replicate high fidelity stroke kinematics obtained using the new Qualysis underwater motion capture system. Surface scans of the arm will provide the local geometry and soft tissue deformations will be assessed through the application of marker clusters to the arm (Warner and Heller, 2016) and the Optimal Common Shape Technique (OCST) (Taylor et al., 2005). This will be compared to full field deformations obtained from underwater Digital Image Correlation (DIC). Soft tissue deformations depend on the muscle activation and the external forces, causing changes to the body shape during swimming which impact on the developed flow features and pressure distribution. The project will develop methods for capturing these complex interactions between internal and external forces, a critical step for estimating the local tissue mechanics in swimming animals more generally. Such quantitative knowledge will inform future treatments and preventative measures to reduce shoulder pain and injuries.
A wider impact of this project will be the development of high fidelity measurement techniques that can be applied to biological or deforming structures. This aligns closely with other focus areas in the Industrial strategy such as robotics and artificial intelligence, where soft robotics are becoming more popular, and the highlighted need to 'provide UK industry with world-leading measurement science and technology'.