50 patients with low back pain were randomized to undergo either high-velocity low-amplitude thrust (HVLAT) rotary manipulation or the McKenzie Extension in Lying manual therapy approach. The study was conducted to assess the effects of these manual therapies on skin conductance, as a measure of sympathetic nervous system activity, which is thought to be the pain processing mechanism of the body. Although both therapies were reported to increase skin conductance (HVLAT to a significantly greater extent), without pain as a measured outcome it was difficult to infer the success of these therapies in low back pain patients.