Shiatsu involves a rhythmic sequence of pressure to unblock and balance flows of life energy, commonly known as "chi." Similar to acupressure and acupuncture, this form of massage focuses on your body's points and pathways considered essential for health and well-being.
The word shiatsu means "finger pressure," so it makes sense that practitioners use mostly finger pads, and no massage oil, while you wear loose cotton clothing. According to MassageTraining101:
The focus is on specific zones on the skin that are located along the energy meridians. When these meridians are unblocked the major body systems and organs they represent are encouraged to heal and attain perfect balance. Shiatsu bodywork brings about a sense of relaxation while stimulating blood circulation and lymphatic flow.
Sounds great, but it still comes with a warning: After their first Shiatsu massage, many clients complain of flu-like symptoms, body pains, or headaches as side effects. (Wait, I thought the purpose of a massage was to relieve aches and pains?!) Thankfully, these symptoms (should) never last long and decrease with each additional treatment.