“…Typically, accuracy has been quantified by comparing joint angles calculated using IMU systems to optical motion capture through root mean squared error (RMSE) [ 10 , 11 ], correlation coefficients [ 12 , 13 ], and/or Bland-Altman limits of agreement [ 14 , 15 ]. Efforts have largely been focused on IMU system validation for lower limb angles during gait [ 16 , 17 , 18 ]. However, other activities, including stair climbing, kicking, materials handling, and skiing [ 14 , 19 , 20 , 21 ] and upper body angles [ 22 , 23 ] have been examined as well.…”