The aim of this study was to determine the variability of the thrust parameters produced by practitioners performing a high velocity spinal manipulative therapy technique (toggle-recoil) normally applied to the neck. Fourteen participants performed three thrust trials, separated by >30minutes, on a patient simulation device. Force and displacement generated during the thrusts were simultaneously recorded and analysed off line. Peak thrust force ranged from 18.2 to 246N with a mean of 111.2N (SD 48.8). Time to peak thrust force ranged from 20 to 100ms, mean 67.5 ms (SD 13.1). Peak thrust displacement ranged from 6.1 to 28.9mm, mean 24.1mm (SD 4.9) and time to peak thrust displacement ranged from 22.5 to 105ms, mean 59.4ms (SD 13.8). This study demonstrates that the force and displacement induced by any individual practitioner on a simulator can vary by up to 50% during a toggle-recoil thrust. Furthermore, different practitioners may vary in their force by as much 100% and in displacement by 50% when the toggle-recoil spinal manipulative procedure is performed.