Fig. 4. Effects of viscosity and longitudinal location on the mean values of kinematics and muscle activity. (A) Lateral vertebral flexion (β_max) is the maximum attained within a cycle. For a single viscosity, flexion was always greatest in posterior sites, but with increased viscosity the largest change in flexion occurred anteriorly. (B) EMG intensity increased significantly with increased viscosity and was commonly greater in more posterior locations. (C) EMG duty factor was nearly constant for all longitudinal sites and viscosities.