Background: Total Hip Arthroplasty (THA) is an effective method for relieving pain and improving gait function. However, THA patients demonstrate slow gait speed at discharge. Rehabilitation programs after THA require the immediate improvement of gait speed early in the postoperative period. To examine the immediate effects of seated side tapping training (SSTT), which focuses on lateral trunk movement and movement velocity, on gait function in early postoperative THA patients, the methods were as follows: The SSTT group performed five repetitions of a task in which they moved their trunks laterally to alternately touch markers to their left and right side as quickly as possible 10 times in a seated position. One set of SSTT lasted approximately 3 min. The control group rested in a seated position for 10 min. Results: Significant interactions were observed for gait speed, stride time, and stride time coefficient of variability. The SSTT group demonstrated significant pre-post-intervention improvement in gait speed, stride time, and coefficient of variability. Conclusions: SSTT improved both gait speed and gait stability and can be performed easily and safely. Therefore, single-session high-velocity trunk training may be an effective method to improve gait function immediately in early postoperative THA patients.

Faster lower-limb motion is closely related to soccer performance, but the contribution of lumbopelvic motion to achieving it remains unclear. This cross-sectional study aimed to examine whether faster lower-limb motion in soccer players was accompanied by greater lumbopelvic motion. Fifty-one male high school soccer players performed a thigh-raising (hip flexion) task from a standing position at low (approximately 100°/s) and high (approximately 400°/s) speeds. Lumbopelvic motion was measured at the lumbar spinous process (L3). Rotation (LBrot, transverse plane) and flexion–extension (LBf/e, sagittal plane) were derived from the angular velocity. Motions were compared between speeds using the Wilcoxon tests. In the dominant leg, both LBrot (10.2° vs. 8.1°, r = 0.62) and LBf/e (6.4° vs. 5.0°, r = 0.57) were greater at high speed. In the non-dominant leg, both LBrot (11.2° vs. 8.6°, r = 0.49) and LBf/e (6.9° vs. 5.3°, r = 0.62) were also greater at high speed. High-speed trials exhibited consistent movement patterns, whereas low-speed trials did not. These findings suggest that minimizing lumbopelvic motion may not always be optimal for achieving faster lower-limb motion, which may inform coaching and clinical practice regarding the appropriate degree of lumbopelvic motion during lower-limb tasks across movement speeds.