Joint amplitude and frequency analysis of tremor activity.

Clinical tremor analysis mostly is used for the measurement of tremor frequency. The analysis is based on short segments of EMG recordings and on clinical ratings of tremor intensity. Accelerometry appears to have some practical advantages. The present study was concerned with the development of a methodology for assessing tremor activity using the three parameters, frequency (Hz), amplitude (g), and occurrence of tremor (in per cent of time). These parameters were derived from joint amplitude frequency analysis of the calibrated accelerometer raw signal and from appropriate decision rules. This methodology was used in connection with 27 patients with Parkinson's disease, to investigate the aforesaid parameters of tremor activity. Postural tremor had a higher occurrence time (right-hand only) and higher frequency (left-hand only) than resting tremor, however, the average amplitudes did not differ. The correlations between right-hand and left-hand measures were higher during postural tremor test. Frequency was not correlated to amplitude or occurrence time, however, moderate correlations did exist between amplitude and occurrence time. In addition to the assessment of tremor activity, multi-channel accelerometry may be used for the detection of posture and motion. Further applications of this methodology, for example, in 24 hr ambulatory monitoring of tremor, are discussed.

Assessment of posture and motion by multichannel piezoresistive accelerometer recordings.

Modern assessment of posture and motion involves the use of wide bandwidth piezoresistive accelerometers. The direct current (DC) component allows for assessment of slow motion and change in position referring to the gravitational axis: the alternating current (AC) component, calibrated in g. represents acceleration along the sensitive axis of the device. A method study was designed to evaluate the division in DC and AC components, reliabilities, discrimination between conditions, and detection of types of physical activities. Recordings were made in 26 student participants for eight conditions: sitting, standing, lying supine, sitting and typing on a PC keyboard, walking, climbing stairs, walking downstairs, and cycling. This procedure was repeated in reversed order. A classification of physical activities according to the eight conditions (first trial) and based on four parameters, that is DC components trunk, thigh, and lower leg and AC component trunk, was correct in almost 100% of patterns, when applied to the second trial.