Objective measurement of functional upper-extremity movement using accelerometer recordings transformed with a threshold filter

Background and Purpose-The consensus is that the most important outcome for rehabilitation is functional activity in the life situation. Constraint-In duced Movement Therapy, a new treatment that transfers in-clinic gains to t he life situation, demands objective measurement of real-world movement. Ho wever, direct, objective, and accurate measures of arm use in the real worl d are not available. Previous attempts to use accelerometry to measure extr emity movement have failed because of unacceptable variability. This proble m has been addressed here by use of a threshold filter. Methods-Nine stroke patients and 1 healthy individual wearing accelerometer s were videotaped while they carried out their usual activities at home or in the clinic; the duration of their arm, torso, and ambulatory movements w as judged by 2 observation teams. In addition, Il college students performe d 5 standardized activities of daily living for varying durations in the la boratory. The accelerometer data were transformed; the raw value recorded f or a given epoch was set to a constant if it exceeded a low threshold. Results-The threshold-filtered recordings measured the duration of movement accurately and with very little variability. Correlations between the thre shold-filtered recordings and the observer ratings of the duration of arm, torso, and ambulatory movements were 0.93, 0.93 and 0.99, respectively; the corresponding correlations for the raw values were -0.17, 0.34, and 0.85. Conclusions-These results present initial evidence for the validity of thre shold-filtered accelerometer recordings for objectively measuring the amoun t of real-world upper-extremity movement as an index of treatment outcome f or rehabilitation patients.