The benefits of walking outside on the brain

The benefits of exercise on cognitive function are well known and well established. However, the environment in which the exercise is performed could play an equally important role as the exercise itself. Some studies suggest that the simple fact of spending time in nature, in the forest or in a green space would have a beneficial effect on cognition of a similar magnitude to that provided by sustained exercise. Are these effects additive? In other words, could exercise performed outdoors be more beneficial for cognitive function than exercise performed indoors, at the gym or at home? This is a question that Canadian researchers attempted to answer recently in a controlled study.

The researchers recruited 32 students from the University of Victoria in British Columbia. This number of participants may seem small, but it is high enough to ensure good statistical power. Participants were asked not to exercise or consume alcohol 24 hours before the test, and not to eat or drink coffee 2 hours before the test. On day 1, participants completed a standard cognition test (oddball task) on an iPad while wearing sensors on their heads to record an electroencephalogram (EEG). This test and the EEG recording were performed before and after doing 15 minutes of exercise (walking) indoors or outdoors. Participants who walked indoors on day 1 walked outdoors on day 2 (2-7 days after day 1) and those who walked outdoors on day 1 walked indoors on day 2 (crossover study design).

The reaction time measured by the test was on average 7.7 milliseconds (ms) faster after walking 15 minutes outdoors than before (213.3 ms vs. 221.0 ms). Conversely, participants who walked indoors had a reaction time only 2 ms faster on average than before walking (218.1 ms vs. 220.1 ms). Statistical analysis of the results indicates that only the difference in reaction time after walking outside is significant. Regarding the number of errors made during the test, there was no significant difference before or after walking, both indoors and outdoors.

EEG results show that the amplitude of the P300 wave (brain activity associated with working memory and attention) does not change significantly after walking for 15 min indoors (1.6 µV vs. 1 .5 µV), but increases significantly after walking 15 min outdoors (2.4 µV vs. 1.4 µV). This 71% increase in the amplitude of the P300 wave reflects an improvement in cognition through outdoor exercise.

Overall, these results suggest that a 15-minute light walk outdoors may have beneficial effects on cognitive functioning. This observation supports the idea that exposure in the natural environment is beneficial for brain health. In a world where people increasingly live in urban settings, less and less time is spent outdoors and exercising indoors (gyms, home exercisers, etc.) is very popular. Exercise is beneficial for cognitive health whether it’s done indoors or outdoors, but why not do it outdoors as often as possible, weather permitting, and thus make the most of the cognitive health benefits?