You might have got too strong pressure during the Shiatsu treatment. Skillful and experienced Shiatsu practitioners know well what kind of stimulation and how much pressure the each patient need. However, unexperienced practitioners or practitioners who like to apply strong stimulation with powerful pressure likely to do Shiatsu for their patients with much stronger pressure than they need. Or your Shiatsu practitioner may not master the basic rules of Shiatsu pressure techniques. Then such a practitioner might have rubbed your muscles and skin with too much pressure. This kind of case is caused by awkwardness or unskillfullness of the Shiatsu practitioner. Then you may feel pains and stiffness after a treatment, and may feel even worse than before you received the treatment. If your Shiatsu practitioner happen to be such a practitioner, do not hesitate to ask him/her to apply more soft pressure Shiatsu and to treat you more gently.