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

Introduction: Parkinson's disease is a chronic and progressive neurodegenerative condition characterized by dopaminergic loss of the substantia nigra. This condition promotes motor symptoms such bradykinesia, rest tremor, rigidity, and postural instability, which can directly interfere on gait performance. The use of physical interventions in shallow water pools is a viable and beneficial option for People with Parkinson's Disease. Aims: The aim was to compare the angular 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 self-selected comfortable speed on 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 walking speed, lower limb joints total range of motion (ROM) and peak angular speed during the stride cycle were calculated. 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: The ROM and peak angular speed from all lower limb joints were similar between groups. With the increase in depth, the walking speed and peak angular speed of ankle reduced in Older (129.4 ± 80.7 to 83.2 ± 23.5 º/s; P = 0.027) and PwPD (137.1 ± 47.7 to 95.0 ± 57.1 º/s; P = 0.012; d = 0.91). Regarding knee, this decrease occurred only in the PwPD group (157.0 ± 34.8 to 131.8 ± 36.8 º/s; P < 0.001). Conclusion: The ROM from all lower limb joints was unaffected in both groups. With the depth increase, we observed a decrease in the walking speed in both groups and a reduction of the peak angular speed from the distal joints of the lower limb (ankle for PwPD and Older, knee for PwPD). The present findings can help professionals of aquatic rehabilitation to choose the best depth and adequately plan exercise programs, according to the main objective of the treatment and the needs of each individual.