Effect of aquatic walking on prefrontal activity and executive function in healthy middle- and old-aged adults: a pilot study

Previous studies have shown that normal and complex land walking (e.g. dual-task and obstacle walk) have a positive effect on the prefrontal cortex (PFC) and executive function. However, little is known about the benefits of aquatic walking. The underwater environment is a complex environment with water flow and resistance. Such an environment may induce different brain responses than the land environment. These responses can possibly affect brain function. Therefore, we hypothesized that aquatic walking enhances PFC and executive function more than land walking. Seven participants (age: 57.6 ± 7.0 years, body mass index: 22.9 ± 4.6 kg m−2) performed walking for 10 mins at a self-selected comfortable speed in both conditions. Then, the color-word Stroop task (CWST) was administered at pre- and post-exercises. The left prefrontal hemoglobin activity was monitored via functional near-infrared spectroscopy during the CWST and walking trial. Stroop interference performance, which reflects executive function, was calculated using reaction time and hemoglobin activity during the CWST. Compared to land walking, aquatic walking enhanced cortical activations and reaction time in the Stroop interference. In addition, aquatic walking was more likely to enhance cortical function than land walking. Hence, aquatic walking can induce higher cortical activation relative to land walking at a similar intensity, and it promotes executive function in healthy middle- and old-aged individuals.