Sharing
Adding your run to part of a reel
To show your run for only part of a video, save its sticker as an overlay: the sticker on a see-through background, kept see-through in Photos.
In the share sheet, pick a sticker and tap Save overlay. Then in your video editor (Instagram Edits, for one), add it from Photos as an overlay and trim it to the seconds you want.
Save image saves the finished picture on a dark card instead, for a post of its own.