How Well iPhones Measure Steps in Free-Living Conditions: Cross-Sectional Validation Study

Shiho Amagasa   ¹ , MMS ;   Masamitsu Kamada   ^{2, 3} , PhD ;   Hiroyuki Sasai   ⁴ , PhD ;   Noritoshi Fukushima   ¹ , PhD, MD ;   Hiroyuki Kikuchi   ¹ , PhD ;   I-Min Lee   ^{5, 6} , MBBS, MPH, ScD ;   Shigeru Inoue   ¹ , PhD, MD

¹ Department of Preventive Medicine and Public Health, Tokyo Medical University, Shinjuku-ku, Japan

² Department of Health Sociology and Health Education, School of Public Health, Graduate School of Medicine, The University of Tokyo, Bunkyo-ku, Japan

³ Department of Social and Behavioral Sciences, Harvard TH Chan School of Public Health, Boston, MA, United States

⁴ Department of Life Sciences, Graduate School of Arts and Sciences, The University of Tokyo, Meguro-ku, Japan

⁵ Division of Preventive Medicine, Brigham and Women’s Hospital, Harvard Medical School, Boston, MA, United States

⁶ Department of Epidemiology, Harvard T.H. Chan School of Public Health, Boston, MA, United States