Shallow water walking at different immersion depths in older adults with and without Parkinson’s disease: spatiotemporal responses.

Introduction: People with Parkinson's Disease (PwPD) have motor symptoms which can directly interfere on gait performance. Considering that PwPD have altered gait, and physical activities in shallow water can promote benefits on the neuromuscular performance, it is important to evaluate the biomechanical effects of different levels of water immersion on the gait biomechanics of PwPD. Aims: The aim was to compare the spatiotemporal responses of shallow water walking at two immersion depths (waist and xiphoid) by older adults with and without Parkinson’s disease. Method: Ten older adults with Parkinson’s disease (PwPD group) and ten older adults without Parkinson’s disease (Older group) were analyzed during shallow water walking at a self-selected comfortable speed on a pool floor in the immersion depths of waist and xiphoid levels The 2D kinematic data from the sagittal plane was recorded with a subaquatic GoPro Hero4 camera. We marked the participants skin with ink on the specific anatomical points. Five strides per condition from each participant were analyzed (total of 196 strides). The anatomical markers from the videos were digitalized with a deep neural network and the metric coordinates from the stride cycle were reconstructed with a direct linear transformation algorithm. The kinematic data analysis was performed in Matlab routine. The raw kinematic data were filtered with a low-pass Butterworth filter. The stride frequency (SF in Hertz) and the stride length (SL in m) were calculated. The duty factor (DF in %) was calculated as the contact phase duration relative to the entire stride cycle. The data are presented as mean and standard deviation. Shapiro-Wilk test was used to test data normal distribution. Paired t-test and independent t-test were used to compare the spatiotemporal and angular variables between depths and groups, respectively. Cohen’s d (depth immersion factor) and Hedges’ g (health condition factor) effects sizes were calculated. Results: In relation to the groups, individuals with Parkinson's Disease presented higher SF (waist: 0.46 ± 0.01 vs. 0.38 ± 0.03 Hz) and xiphoid: (0.40 ± 0.00 vs. 0.37 ± 0.04 Hz) and lower DF (waist: P = 0.002 and xiphoid) than the Older group in both depths and also lower SL in waist depth (0.51 ± 0.12 vs. 0.65 ± 0.14 m). Regarding depth, it is noted that the increase in depth presented lower SF for the PwPD group (P < 0.001), lower SL for the Older group and lower DF for both (Older: 73.5 ± 2.4 to 69.6 ± 1.6 %) and PwPD: 70.7 ± 0.3 to 68.3 ± 0.4 %). Conclusion: It is noticed that when individuals with Parkinson's Disease walk in greater depth, they decrease the cadence, and the stride length, consequently staying with the foot less time on the ground, precisely to be able to walk and overcome the depth, maintaining balance. The present findings may help aquatic rehabilitation professionals choose the best depth and plan exercise programs, according to the treatment's main objective and each individual's needs. Agradecimentos: Agradecemos às instituições de ensino que disponibilizaram espaços e materiais para a elaboração e desenvolver da pesquisa (Universidade Federal de Ciências da Saúde de Porto Alegre (UFCSPA) e Universidade Federal do Rio Grande do Sul (UFRGS)).