Tominaga, R, Ishii, Y, Ueda, T, and Kurokawa, T. The effects of running speed on ground reaction forces and lower limb kinematics during single-leg stop movement. J Strength Cond Res 30(5): 1224–1230, 2016—The purpose of this study was to investigate the effects of running speed on both ground reaction forces (GRFs) and lower limb kinematics during the deceleration phase of the single-leg stop movement. With 7 male university students participating in this study, each subject accelerated forwards at 3 approach speeds (2.50, 2.75, and 3.00 m·s−1), and stopped with the right leg landing on the force plate. Kinematic data were recorded from a lateral view using 1 high-speed camera. The result was that all subjects indicated the same stopping pattern, and 3 peaks of the resultant GRF were observed. The first peak (P1) appeared before full foot-ground contact, and the time to peak from initial foot contact to P1 was significantly shorter with increasing approach speeds (p ≤ 0.05). The second (P2) and third (P3) peaks were observed after full foot-ground contact, and the resultant GRF at P3 and the posterior GRF at P2 and P3 were significantly greater with increasing approach speeds (p ≤ 0.05). The hip flexion and the planter flexion angles at each peak were larger with increasing approach speeds (p ≤ 0.05). However, there was no significant difference in the vertical GRF, range of motion, and angular velocity of hip, knee, and ankle joints when comparing different approach speeds. This study suggests that to improve the stop movement strategy under faster approach speeds, it is important to increase the magnitude of posterior GRF and the hip and ankle flexion angles under increasing speeds.