The Influence of the Aquatic Environment on Quasi-Static and Dynamic Domains of Posture: Towards Applications for Spinal Cord Injury Aquatic Rehabilitation

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PROQUEST: 2082274529

Abstract

The objective of this thesis was to investigate the direct effects of the aquatic environment on quasi-static and dynamic domains of posture in able-bodied individuals and individuals with incomplete spinal cord injury (iSCI). The first and third studies (Chapter 2 and 4) investigated the influence of water immersion on postural sway during quiet standing of able-bodied participants. Time-domain measures of the center of pressure (COP), i.e. COP amplitude, velocity and area, revealed that individuals swayed more in water than on land. The frequency-domain parameters showed a predominance of low frequency sway in water. Further, a different postural strategy to maintain balance in water was detected: (i) individuals leaned more forward, (ii) mediolateral upper trunk instability was increased, and (iii) eyes closed in water led to increased mean velocity and sway area. The second and fourth studies (Chapters 3 and 5) demonstrated the effects of the aquatic environment on gait initiation among able-bodied participants. COP trajectories during anticipatory postural adjustments and execution of the first step were longer in length and time to execute in water than on land. Individuals adjusted their posture more rapidly in water prior to step execution, but the execution of the first step in water was slower than on land. Absolute and body-weight-normalized impulses demonstrated increased anteroposterior impulses showing a clear influence of water resistance, and decreased vertical impulses demonstrating the effect of the water buoyant force. The upper to lower trunk acceleration ratio in anteroposterior direction also increased under the effect of the immersion in water demonstrating the influence of water resistance on the lower body. The last two studies (Chapters 6 and 7) revealed that COP sway was larger when individuals with iSCI stood quietly in water, and that gait initiation performance was similar to the able-bodied participants, especially in individuals with high-functioning balance performance. The aquatic environment appeared to have challenged but also supported quasi-static standing and gait initiation in both able-bodied individuals and individuals with iSCI. Overall, individuals with iSCI felt safer performing standing and gait initiation in water than on land, with the exception of one participant with extensive sensory deficits.

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