Reaching down

On my way to swimming I was aware that I had a stiff left shoulder and gradually realised that it was probably due to carrying a box around the University this morning. It was a light box but  little large and unwieldy. The swimming instructor noticed my stiffness and encouraged me to try to roll more and reach downwards more on every stroke. I did gradually loosen up and noticed that when the 'reaching' went well the strokes felt more efficient and powerful but not more tiring. On quite a few occasions I managed pairs of bilateral breathing lengths. If I could maintain the style I should be able to do more lengths consecutively.