If that just happened recently, you better get that checked. Being in good health not necessarily means that you did not suffer any injury in your back. Had that problem a few months back, and it turned out that my back got strained from all the gear that I carry (not to mention the hell of stress I'm getting from work). A few sessions with a PT did the trick for me.I keep up on the exercise daily (even on the weekends) and I am in generally good health per my doctor but something lately is weird with my back. I can not fully stretch so I do not get it. Should I be doing more warm ups before we head out for a hike?