If you've ever felt calmer after a walk in the park or a stroll through the woods, it's not your imagination - it's biology. Being outdoors can trigger measurable changes inside your body from lowering stress hormones, easing blood pressure and even improving your gut health. You don't have to hike for hours to feel these benefits as maximum impact happens after just 20 minutes, so even a lunchtime walk to the park and a sandwich on a bench a few times a week can benefit your body and mind.