Low back pain (LBP) is a well-recognized health problem. One common manual therapy available for the treatment of LBP is spinal manipulation (SM), which can be separated into 2 categories: High-Velocity Low-Amplitude (thrust) and Low-Velocity (non-thrust) SM according to their force-delivery profiles. One commonly utilized non-thrust SM technique is the Flexion-Distraction procedure. Several studies have reported manually applied forces during thrust SM; however, the forces used during non-thrust SM, specifically those used with Flexion-Distraction treatment are still unknown. The results of this pilot study will provide preliminary information on treatment forces and sample size justification for future full-scale trials, while also ascertaining the feasibility of the study protocol and patient recruitment methods for such trials.