RESEARCH REPORT POSTER DISPLAY

DEVELOPMENT OF A MANUAL THERAPY TOOL WHICH COULD FACILITATE APPLIED FORCE CONTROL WHILE MAINTAINING SENSITIVITY. Diong J¹, Waddington G², Adams R³; ¹Liverpool Hospital, NSW, Australia. ²Physiotherapy School of Health Sciences, University of Canberra, ACT, Australia. ³School of Physiotherapy, University of Sydney, NSW, Australia

PURPOSE: During manual therapy, the hands are used to assess and reassess stiffness in the spine, and mobilization forces are both applied and absorbed by the hands. Therefore, factors that alter the force produced when force constancy is intended are important, because unintentionally high force could injure the hands. Accordingly, a manual therapy/mobilization tool was designed, to better spread these forces over the hands, and to show the amount of force being applied. RELEVANCE: Although therapist and patient positioning within the clinic is variable, effects of therapist posture on control of applied force are unknown. The tool was thus used to determine whether (i) sensitivity to differences in stiffness when using the device is changed from the same stiffness assessment conducted with the hands alone, and (ii) force constancy can be maintained with variations in posture. PARTICIPANTS: A convenience sample of 30 subjects recruited from the third-year undergraduate and postgraduate student body of the University of Sydney’s Faculty of Health Sciences participated in the study. METHODS: Subjects were tested to measure their discrimination, without feedback, between different elastic stiffnesses. Stiffness assessment was conducted when using the manual therapy tool and also with the hands alone. In addition, subjects attempted to maintain force constancy during a series of Grade II and IV mobilizing forces applied using the mobilizing tool on a plinth. The point of application of these forces was at varying distances from the body, and no feedback was given. ANALYSIS: A matched pairs t test was used to compare sensitivity of stiffness discrimination with and without the use of the mobilizing dynamometer. To examine the effect of posture on force application, a repeated-measures analysis of variance was used. RESULTS: Stiffness discrimination was not significantly different whether the hands or the device was used (t₂₉ = −0.986, p = 0.332). Also, force constancy was maintained at Grade II when the point of force application was moved away from the body, but subjects were unable to replicate their Grade IV mobilization forces in similar postures, despite an increase in perceived effort (F_1,29 = 18.622, p < 0.001). Both within and between subject variation in force produced for both grades of mobilization was substantial, although subjects were trying to produce the same force for each grade. CONCLUSIONS: Subjects are equally good at discriminating between different stiffness levels whether the hands or the tool is used. Also, consistency of application of force cannot be maintained with changes in posture. IMPLICATIONS: Variations in applied force observed with different therapist postures could be controlled if force read-out was available on a mobilization tool, and use of this tool in elastic stiffness discrimination did not inhibit sensitivity compared to use of the hands alone. KEYWORDS: Manual therapy, Mobilization, Tool use. FUNDING ACKNOWLEDGEMENTS: Not applicable. CONTACT: Gordon.Waddington@canberra.edu.au

ETHICS COMMITTEE: University of Sydney Human Ethics Research Committee