METHODS: Thirty-three chiropractic students simulated a high-velocity low-amplitude prone thoracic spine manipulation. Three force goals based on percent of maximum thrusting ability were used in blocked and random variable practice. Participants received either visual feedback or knowledge of performance feedback regarding their force-time history. Serial retention tests without feedback followed blocked and random variable practice. Peak and average rates of thrust development, as well as the constant error, absolute constant error, and variable error of peak force production, were calculated.
CONCLUSION: Familiarity and practice of high-velocity low-amplitude spinal manipulation resulted in greater accuracy of peak force production. Lower error scores were observed in acquisition with blocked variable practice. However, short-term accuracy was enhanced in retention when participants had used random variable practice. Random variable practice combined with visual feedback improved force production accuracy in retention. The variability of peak force production increased to 61% of maximum thrusting ability and then decreased. The greatest accuracy with least variability of peak force production was seen near 75% of maximum thrusting ability.
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