Thumping while playing

I have a 1 year old female rabbit, un spayed, and when she's showing signs of happiness, I.e. running and jumping, she thumps. I've been trying to figure out if this is because she's scared of something or doing because she's that happy.

Thumping is tied to more than just a rabbit being scared. It pretty much has to do with them feeling strong emotion. So when they are scared, on alert, irritated, and yes, even happy.

Usually when they are thumping because they are scared, they will also freeze in place or run and hide, and their ears will be up and alert(for uppy eared rabbits) and their eyes will be wide open. When they are happy and thump, they will just run around continuing to play. Some of my rabbits will thump too, when they are running around playing.

I was just going to post this same question! My Graham will run circles around me and then make his usual run through his xpen and back out and over to a runner rug and back to my feet. He's done this for a long time. Recently he's added a thump here and there. I was getting concerned but he also seems so happy. I thought maybe he was telling my husband that "she's mine"! Lol. He's 4 months old and set to get fixed in a course le of weeks. Any additional thoughts?? Thanks!