Methods: Fifty volunteers (17 women and 33 men) from a Canadian chiropractic college participated in this study. Participants were block randomized into 5 cohorts of 10 subjects, representing years 1 to 4 and graduates with more than 5 years of practice experience. Participants performed a hypothenar transverse push procedure on the upper thoracic spine, with the subjects lying on a force-sensing table. The average of 3 force-time profiles of the procedures was compared across cohorts using analysis of variance for differences between groups, and pairwise comparisons by Scheffé test, using Holms method for P value adjustment.
Results: Peak force, force rate, and rise time revealed strong differences based on cohort (P < .001). A natural maturation in high-velocity, low-amplitude force development occurs during training. Little change in peak force occurs in the first 2 years. The majority of development occurs in year 3, with tapering through year 4. A reciprocal coupling exists between peak force and force rate.
Conclusions: Group means revealed statistically significant and monotonic increase in force rate, a decreased rise time, and decreased peak force during delivery of the therapeutic peak force. These differences paralleled growth in experience but with an asymptotic leveling of change between the fourth year of training and 5 years of clinical practice experience. This study showed a systematic maturation in performance associated with educational experience. The reciprocal coupling between rate of force development and peak force created a relatively stable impulse.
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