 Subjects were randomized into one of two treatment sequences: pregabalinactive placebo or active placebopregabalin. Each arm lasted 10 days, with a washout period of 10 days between treatments. Pregabalin was administered as a standardized two step titration, starting at 75mg twice daily up to a maximum daily dose of 150mg twice daily; and likewise, diphenhydramine active placebo was administered starting at 6.25mg twice daily up to a maximum daily dose of 12.5mg twice daily. The primary endpoint was time to first symptoms of moderate intensity NRS 410 during treadmill ambulation. Ambulation assessment was performed during the screening visit, and on day 10 of each period to evaluate pain intensity associated with walking as well as distance covered by the patients. Quantitative assessment of ambulation was conducted on a treadmill at 0 ramp incline at 1.2 miles per hour mph. Measurement of self-reported symptom severity using the NRS at baseline, and every 30 seconds for a maximum of 15 minutes was recorded. The following information was also recorded: time to first symptoms, total ambulation time. The examination was stopped after 15 minutes or at the onset of severe symptoms. Severe symptoms were defined as the level of discomfort that would make patients stop walking in usual life situations. No one was encouraged or prompted to continue walking beyond this point. Patients were instructed to walk with an upright posture. They were not permitted to lean forward or hold onto the handrails during the examination. Secondary outcome measures included area under the curve of present pain intensity with ambulation at each specified time point, final pain intensity with walking, walking tolerance, time to return to baseline pain level after ambulation, as well as the results of a series of pain related questionnaires including: Visual Analog Scale VAS, Patient Global Assessment PGA, NRS, Roland Morris Disability Questionnaire RMDQ, modified Brief Pain Inventory short form mBPI-sf, Oswestry Disability Index ODI, and Swiss Spinal Stenosis SSS. 