Frequency analysis of commercially available vibrators

The tonic vibration reflex -- elicitation of a muscle contraction by mechanical vibration -- is a well documented physiological phenomenon of particular relevance to physiotherapy. Among the critical features pertaining to the effectiveness of its use in clinical practice are the mechanical attributes of the vibrator used to elicit the reflex. Because physiological responses differ with vibrations of varying frequency and amplitude, it is necessary to measure these characteristics before a commercial vibrator is used therapeutically: Facilities and equipment for performing such tests are, however, not readily available to physiotherapists. The purpose of this study, therefore, was to measure and compare frequencies of a variety of commercially available vibrators under varying load conditions and over time. Vibrators from major Canadian retail outlets and manufacturers were obtained and, through the use of both mechanical and optical methods, a total of 19 models were frequency-calibrated. The results of the study permit discussion related to the suitability and reliability of each model and provide specific guidance to physiotherapy departments in the selection of appropriate therapeutic vibrators. The results also indicate that the mode of application, such as strapping the apparatus to the patient rather than having the operator hold it in her hand, affects the frequency in some models. The data related to frequency measurements, gained through this study, should enable therapists to make more effective use of commercially available vibrators in motor reeducation.