The next stage in the class is usually a period of exercises that give the body a warm-up and stretch in preparation for the physical activities which will follow, but more importantly, they are designed to focus ones mind on, and develop the students 'centre'. The easiest way to explain this is to say that most of the power in Aikido comes from your centre. Quite literally the centre of the body, you don't require bulging biceps and thighs of steel to practice Aikido. It is for this reason that it is an ideal pursuit for men, women, young, old, large and small. This stage of the class can last from 5 minutes to half an hour and usually involves everyone spread out on the mats doing the exercises that Sensei is demonstrating in front of them.