OBJECTIVE: a) Establish a precise, standardized method to assess prone leg alignment changes (functional "leg length inequality"), which have, until now, been reported clinically to occur as a result putative chiropractic subluxation isolation tests [neck flexion (C5) and extension (C1)]; and b) describe differences in leg alignment changes in a group of healthy subjects and patients with chronic spinal complaints.

DESIGN: Two group, two isolation tests, descriptive, repeated measure analysis of variance.

SETTING: Exercise and Sport Research Institute, Arizona State University.

PARTICIPANTS: Eight healthy controls, eight patients with a history of chronic spinal complaints and observable leg alignment reactivity.

INTERVENTIONS: Active cervical flexion/extension maneuvers.

OUTCOME MEASURES: Optoelectric markers affixed to heels and occiput, as subjects lay prone. Marker locations sampled at 100 Hz for 10 sec during: a) three no movement trials, b) three cervical extension and c) three flexion trials. Data transformed to local reference frame approximately each subject's longitudinal axis prior to analysis.

RESULTS: Heel position movement occurred during trials and were highly individualistic. Patients exhibited more asymmetrical movements than the controls during the head-up trials. No differences existed between controls and patients for range of heel displacement or net displacement.

CONCLUSIONS: The results of this study allow the following to be concluded: 1) small leg displacements (< 1 mm) were recorded by the optoelectric measurement system; 2) heel position changes during isolation tests were identifiable; 3) as a result of head-up maneuvers, patients exhibited more asymmetrical heel movement than controls (t = 8.743, p < .01); 4) The heel range of motion was not different between the groups; and 5) The net change in heel position was not different between the groups. Patients exhibited more asymmetrical heel motion during head-up isolation tests, suggesting that some phenomena may separate these two groups, warranting future study.

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