In addition to the duration and intensity of your daily activities, Oura tracks the time you spend sitting, standing or otherwise passive, and guides you to break up long periods of inactivity. Moving around, stretching or taking walking breaks regularly helps you stay healthy, and helps keep your metabolism active throughout the day.
By default you get an inactivity alert after 50 minutes of inactivity. Once the inactivity alert goes off, you have 10 minutes to react to it. You can reset the alert by taking a 2-3 minute walk, or moving and stretching for a couple of minutes. If your break is intensive, an even shorter time can reset the inactivity counting.
Check this article to learn more about controlling notifications.
An hour of inactivity will not have a significant effect on your activity score, but if you're still for several hours, the Move Every Hour contributor will gradually start to take your score down.