Latimer, J, Adams, R & Lee, M 1998, 'Training with feedback improves judgements of non-biological linear elastic stiffness', Manual Therapy, vol. 3, no. 2, pp. 85-89.
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A recent unsuccessful attempt to train physiotherapy students to accurately judge lumbar posteroanterior (PA) stiffness may have been due to the students inability to learn to judge a basic component, i.e. linear elastic stiffness. The current study investigated whether an equivalent amount of training with feedback as used in a previous study, improved the same students' ability to judge linear elastic stiffness. The four third-year physiotherapy students from the previous study participated. Students rated the stiffness of 76 stimuli (metal springs) during pre-test, training and post-test sessions held over a 3.5 week period. During the training, trial-by-trial feedback was given regarding the accuracy of their judgements. A paired t-test demonstrated a significant reduction in absolute error between the pre-test and the post-test (P < 0.05). Immediate quantitative feedback training improved physiotherapy students' ability to judge linear elastic stiffness.
Latimer, J, Lee, M & Adams, RD 1998, 'The effects of high and low loading forces on measured values of lumbar stiffness.', J Manipulative Physiol Ther, vol. 21, no. 3, pp. 157-163.
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OBJECTIVE: One explanation for the poor reliability of manual judgments of posteroanterior (PA) stiffness may be that if manual therapists use different forces when testing, different stiffness is perceived. This study was conducted to examine measurements of lumbar PA stiffness obtained using a device programmed to generate different loading forces. SUBJECTS: Twenty-five subjects with no history of low back pain and a mean age of 23.5 yr were measured. METHODS: Measures of lumbar PA stiffness were obtained using a mechanical device that applied a testing force of 200 N to the skin overlying the L3 spinous process. Six stiffness coefficients were determined from the force/displacement curve obtained from each subject by performing linear regressions from 30-80 N, 30-150 N, 30-200 N, and from 30-83.3 N, 83.3-136.7 N, and 136.7-200 N. Intraclass correlation coefficients and repeated measures analysis of variance were used to analyze the data. RESULTS: Although moderate reliability [ICC 2,1 = 0.67] was found for stiffness measures arising from increasingly wide force-interval regressions (30-80 N, 30-150 N, 300-200 N), poor reliability [ICC (2,1) = 0.39] was found for stiffness measures arising from same-width, higher force regressions (30-83.3 N, 83-137 N, 137-200 N). In both cases there were significant differences between the obtained K stiffness values corresponding to different force intervals. CONCLUSION: These results show that if therapists push harder, different stiffnesses will be felt. Studies using instrumental measurement of spinal stiffness to obtain 'K' values should report the force intervals used. Also, revised protocols for manually judging PA stiffness should ensure that stiffness is assessed by sampling specified force intervals rather than the raters determining their own force limits.
Lee, M, Steven, GP, Crosbie, J & Higgs, RJED 1998, 'Variations in Posteroanterior Stiffness in the Thoracolumbar Spine: Preliminary Observations and Proposed Mechanisms', Physical Therapy, vol. 78, no. 12, pp. 1277-1287.
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Background and Purpose. Evaluation of posteroanterior (PA) movement in the spine is commonly used in the clinic, but little is known about the mechanisms involved. The purposes of this study were to examine variations in PA stiffness along the thoracolumbar spine and to investigate possible factors that might determine the pattern of stiffness. Subjects. Twenty-one pain-free volunteers (10 male, 11 female), aged 18 to 41 years (X̄=26.6, SD=7.5); participated. Methods. Posteroanterior stiffness was measured at 5 locations (L4, L1, T10, T7, T4), together with various subject characteristics. Results. Mean PA stiffness varied among locations, with the greatest stiffness at L4 (13.3 N/mm) and the lowest stiffness at L1 (10.4 N/mm). A relatively small, but important, proportion (22% or less) of the variance in stiffness data at some vertebral levels was accounted for by the variables describing subject characteristics. Conclusion and Discussion. Posteroanterior stiffness varies along the spine in a manner consistent with the nature of support for the spine. The observed pattern of variation of PA stiffness along the spine appears to be influenced by some factors other than those relating to the spine. [Lee M, Steven GP, Crosbie J, Higgs RJED. Variations in posteroanterior stiffness in the thoracolumbar spine: preliminary observations and proposed mechanisms.
