The effect of green walking on heart rate variability: A pilot crossover study.

We investigated the effects of regular walking in green and suburban environments on heart rate variability (HRV) and blood pressure (BP) in middle-aged adults. Twenty-three adults participated in a non-randomized crossover experiment comprised of once-weekly 50-min moderate-intensity walking sessions. Separated by a two-week washout period, participants walked for three weeks in each of two treatment conditions (green and suburban) in a local arboretum and suburban sidewalks of Chaska, MN. Eleven participants completed green walking first and 12 suburban walking first. Walks were split into 15-min intra-walk phases, with phases representing each walk's beginning, middle, and final 15-min. Repeated measures linear mixed models evaluated (1) HRV phase differences between treatments and HRV change within treatments, and (2) pre- and post-walk BP differences between treatments and pre-to post-walk BP changes. Intra-walk phase analyses revealed higher HRV during green walking vs. suburban walking during phase 2 (p < 0.0001) and phase 3 (p = 0.02). Less HRV reduction was seen between intra-walk phases 1 and 2 during green vs. suburban walking (p = 0.02). Pre-to post-walk changes revealed decreased mean systolic BP for both green (p = 0.0002) and suburban (p = 0.003) walking conditions, but not for diastolic BP. Post-walk BP results were similar after both green walking and suburban walking. In summary, walking sessions in a green environment elicited greater beneficial HRV responses compared to a suburban environment. Additionally, walking in either environment, green or suburban, promoted reductions in systolic BP.