The purpose of this study was to investigate the effects of chiropractic low back adjustments on thigh muscle strength. Force production was measured during different types of muscle contractions with a device called an isokinetic dynamometer. The study included 21 college-aged subjects who did not have any pain and had never received chiropractic treatment with spinal manipulation. During two separate sessions, subjects' thigh muscle forces were recorded while performing maximal muscle contractions on the isokinetic dynamometer. Baseline measurements of muscle force were acquired before either treatment form of spinal manipulation or a sham spinal manipulation, followed by identical muscle force measurements within five and twenty minutes post-treatment.