Objective: The purpose of this study was to investigate the effects of lumbar rotational manipulation and lumbar central posteroanterior mobilization on lumbar bending stiffness and flexion and extension range of motion (ROM). Methods: A same-subject, repeated-measures, crossover design was used using 32 asymptomatic subjects (16 female and 16 male; mean [SD] age, 25.5 [4.5] years; weight, 65.7 [11.8] kg; and height, 1.70 [0.08] m). Each subject received mobilization or manipulation on 2 different occasions. Bending stiffness was calculated using a 3-point bending model using an electromagnetic tracking device and a force platform; lumbar flexion and extension ROM was measured using an electromagnetic tracking device. All variables were measured pre- and postintervention. Their effect was compared using paired t tests. Results: Manipulation and mobilization did not significantly alter either bending stiffness or lumbar flexion and extension ROM (mobilization: P = .175, P = .613, and P = .535; manipulation: P = .973, P = .323, and P = .439). Bending stiffness changes were not correlated to changes in ROM (Pearson r for stiffness-flexion = -0.102, P = .586; Pearson r for stiffness-extension = 0.014, P = .941). Conclusions: Manipulation and mobilization had no significant effect on bending stiffness or flexion and extension ROM for this group of subjects. Some individual variations in effect were observed.