Mon 13-Aug-12 11:54 AM | edited Mon 13-Aug-12 11:56 AM by Blondul
Thank you very much for the answer, Michael!
The back pain gave away to three days after I returned from vacation. It was a muscle that remained contracted after "efforts" to carry backpack. The windy weather in Paris at that time combined with the sweating under the backpack, contributed to muscle contraction.