Oh My Aching Back!

For some unknown reason my lower back is aching today.  I really did not do anything out of the ordinary to make it feel this way.  I walked 3 miles today indoors, "A Leslie", and instead of her "boosted walking" segments I just did "invisible jump roping".  I like jump roping, I would like to see how long I could jump rope with out dying....maybe that is why my lower back is aching ....I jumped rope today for about 10 minutes total.... oh, and some t-tapp abs!