Kinetic parameters during land and water walking performed by individuals with Down Syndrome

Background: Down Syndrome (DS) is a genetic condition presenting delay in acquisition of main motor milestones, such as walking. Although studies have been investigating the biomechanical parameters during land walking performed by individual with DS, the literature is scarce regarding kinetic parameters analysis in this population, specially during water walking. Research question: This study sought to assess the vertical ground reaction force (Fz) of walking performed in water and on land at different speeds by individuals with DS. Methods: Fourteen adults with DS (age: 27.9 ± 7.9 years; body mass: 58.4 ± 12.9 kg; height: 1.4 ± 0.1 m, body mass index: 29.2 ± 5.4 kg.m-2) completed two sessions of data collection, one on land and another in aquatic environment. The protocol consisted of walking performed at three self-selected speeds (slow, comfortable and fast) in randomized order. The Fz was assessed with a waterproof force plate in each condition. Two-way repeated-measures ANOVA (environment and speed), with Bonferroni's post hoc tests, were used for analysis. A significance level was set as α = 0.05. Results: Significant differences were observed between environments (p < 0.001), with reduced first peak of Fz (68-73%), second peak of Fz (66-70%), loading rate (75-78%) and impulse (40-41%) in the water walking for all speeds analyzed. In the aquatic environment, no significant difference was observed for the first and second Fz peaks with the increasing speed of walking. Moreover, the loading rate significantly increased (p = 0.019) as the impulse significantly reduced (p < 0.001) in the higher speeds. Significance: Individuals with DS present reduced Fz outcomes during water walking in comparison to land. Therefore, water walking may be performed by individuals with DS with safe vertical loads on lower limbs regardless the self-selected speed for rehabilitation, correction of gait and training purposes.