EMG muscle scanning: comparison to attached surface electrodes

EMG scanning norms: caveat emptor

Questions are raised as to the appropriateness of applying static normative data to EMG muscle scanning and whether currently available normative data meet standards prescribed by the principles of measurement. Potential sources of systematic measurement error emanating from hardware differences, the practitioner, and the standardization sample are also discussed. An alternative to the fixed normative approach is presented. Specifically it is suggested that raw EMG data values be scaled using a nonlinear data transformation which would result in a derived standard scan score scale. This would also allow for intermuscular and interindividual comparisons, which are not appropriate with the currently used fixed normative approach. Further, the alternative approach adheres to the principle that EMG data must be interpreted relatively and not absolutely. It is argued that this alternative would eliminate systematic error problems with regard to hardware differentials and preclude the necessity of, and the problems endemic to, norms development. Finally there is an explanation on how one could develop a muscle scanning profile similar to that in current use by many personality inventories. The profiles could then be used as normative.