Effect of central motor and neuromuscular impairment on freestyle swimming technique and performance

Lee, Yu-Hsien (2024) Effect of central motor and neuromuscular impairment on freestyle swimming technique and performance. Doctoral thesis (PhD), Manchester Metropolitan University.

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Abstract

Evidence-based classification is required in Para swimming to ensure athletes are not disadvantaged when competing against others in their allocated class, but there is a dearth of research on how central motor and neuromuscular impairment (CMNI) impacts a swimmer’s movement in the water. CMNI encompasses brain injury, spinal cord injury, as well as other neuromuscular disorders which affect the ability to coordinate movement. This thesis aimed to improve understanding of how CMNI influences freestyle swimming technique and the impact it has on performance. In study 1, analysis of 223 race performances showed stroke length rather than stroke frequency was the main factor limiting CMNI freestyle performance. In studies 2–5, three-dimensional motion analysis was utilised to establish freestyle biomechanical characteristics of highly trained CMNI (30) and non-disabled (13) swimmers. Study 2 examined upper limb, lower limb and trunk kinematics in front crawl; study 3 investigated body roll kinematics; study 4 determined intra-cyclic speed fluctuation, Index of Coordination and Froude efficiency. The final study focused on the kinematics of double-arm backstroke, a specialist freestyle technique. Compared to the non-disabled group, CMNI swimmers displayed irregular hand and wrist positions, shallow and short hand trajectories, restricted elbow and shoulder range of motion, atypical body roll profiles, affected function of upper and lower limbs, and less horizontally aligned body orientations. More impaired swimmers exhibited higher body inclination angles, greater intra-cyclic speed fluctuation and lower swimming speed, stroke length and Froude efficiency than less impaired swimmers. These results indirectly highlight the impact of impaired active range of motion, poor coordination and affected strength on CMNI freestyle kinematics and indicate that CMNI swimmer performance is likely limited by a reduced ability to generate propulsion, minimise drag and swim economically. A high heterogeneity existed in their activity limitations due to the nature of CMNI comprised of various type and severity. This thesis has contributed to knowledge of the biomechanical determinants of CMNI freestyle and thus may inform the development of a more evidence-based Para swimming classification system.