Sentence:  The upper <WSD>backstretches</WSD> require that you stand in position with your feet at a slight distance apart 'than shoulder-width, while the knees are bent slightly.' Intertwine the fingers and then 'push your hands as far away from' the chest area 'as feasible.' 
Meaning of the word marked with <WSD> tags:  An exercise that stretches the muscles of the back.