An exploratory open-label human clinical study was performed in healthy adults with shoulder stiffness to evaluate the efficacy of Astaxanthin by means of measuring blood flow change in the shoulders and subjective questionnaires on physical conditions, including alleviation of stiffness before and after treatment. Two capsules containing 3 mg Astaxanthin each (6 mg in total) were administered once daily (6 mg a day) on days 1 to 28 (4 weeks) to 13 patients (3 men/10 women). All patients were assessed for efficacy and the study demonstrated significant improvements in physical conditions such as shoulder stiffness, physical fatigue, sense of mental irritation, sense of coldness in hands and feet, eye fatigue and eye bleariness. Significant increases of blood flow in shoulders were observed at the end of treatment using laser-doppler graphics. Blood tests conducted to confirm safety before and at the end of treatment showed no clinical differences, and no adverse side effects were reported. In conclusion, Astaxanthin appeared to safely alleviate stiff shoulders and improve other physical conditions during a 4-week open-label study.