ARM IMPAIRMENT AND WALKING SPEED EXPLAIN REAL-LIFE ACTIVITY OF THE AFFECTED ARM AND LEG AFTER STROKE

ObjectiveTo determine to what extent accelerometer-based arm, leg and trunk activity is associated with sensorimotor impairments, walking capacity and other factors in subacute stroke.DesignCross-sectional study.PatientsTwenty-six individuals with stroke (mean age 55.4 years, severe to mild motor impairment).MethodsData on daytime activity were collected over a period of 4 days from accelerometers placed on the wrists, ankles and trunk. A forward stepwise linear regression was used to determine associations between free-living activity, clinical and demographic variables.ResultsArm motor impairment (Fugl-Meyer Assessment) and walking speed explained more than 60% of the variance in daytime activity of the more-affected arm, while walking speed alone explained 60% of the more-affected leg activity. Activity of the less-affected arm and leg was associated with arm motor impairment (R² = 0.40) and independence in walking (R² = 0.59). Arm activity ratio was associated with arm impairment (R² = 0.63) and leg activity ratio with leg impairment (R² = 0.38) and walking speed (R² = 0.27). Walking-related variables explained approximately 30% of the variance in trunk activity.ConclusionAccelerometer-based free-living activity is dependent on motor impairment and walking capacity. The most relevant activity data were obtained from more-affected limbs. Motor impairment and walking speed can provide some information about real-life daytime activity levels.LAY ABSTRACTActivity data from accelerometers can help clinicians to better understand factors limiting physical activity levels. This study aimed to determine to what degree arm, leg and trunk activity, measured with accelerometers, is associated with sensorimotor impairments, walking and other factors in people with stroke in the subacute stage of recovery. Real-life activity, measured by accelerometers, was primarily associated with motor impairment and walking speed. Spasticity, dependency in walking, and disability level also showed association with real-life activity, although to a lesser degree. Accelerometers, placed on the more-affected wrist and ankle, provided most relevant clinical information and are therefore recommended for research and clinical practice. The strong associations observed in this study suggest that when accelerometers are not available, clinical assessments of arm motor function and walking speed can provide some information on real-life activity levels in people with stroke.Key words: stroke, accelerometry, clinical research, rehabilitation, ambulatory monitoring, wearable technology, outcome assessment (healthcare), outcome measures

Individuals with stroke spend approximately 70–80% of their daytime in sedentary activities, and, when active, their activity level seldom reaches moderate-to-vigorous levels of intensity (1–3). To better understand which factors limit activity levels, wearable devices for movement monitoring, such as accelerometers, can be used effectively (4–6). Interest in using wearable technology for quantification of activity and motor function in real-life activities after stroke is increasing within the field of neurorehabilitation (7–9), although application in clinical practice is sparse (7, 10, 11).The Fugl-Meyer Assessment (FMA) is one of the most widely used clinical scales to assess sensorimotor function after stroke. The FMA has excellent psychometric properties (12, 13) and is commonly used as reference when validating new instruments. In addition to motor impairment, sensory function, spasticity, walking ability and speed are commonly assessed in clinical practice after stroke. In general, clinical assessments rely on therapists’ observational skills, and the scoring is limited to predefined categories of the scale. Traditional clinical assessments provide a snapshot of how the patient is functioning at the time of testing, which does not always overlap with the real-life functioning in daily activities (7, 8). Here accelerometers can offer several advantages, by measuring movements and activity continuously over a defined period of time in free-living conditions, and providing an objective measure of motor functioning (9, 14). Such measurements are complicated by the fact that there are numerous different accelerometer devices available, the placement of devices differs, and the metrics obtained are diverse. To overcome this limitation, the use and reporting of accelerometer data in acceleration metrics (m/s²) is advocated to allow comparison between systems, studies and conditions (10). Even though the number of studies using accelerometers is increasing, the validation of the obtained measures is critical for meaningful use in clinical research and practice (14, 15).Moderate-to-strong correlations have been reported between accelerometer-based activity measures and FMA scores (16, 17) as well as Action Research Arm Test (18) among stroke-survivors at different phases of recovery after stroke. Accelerometer-based arm ratio (i.e. the ratio between more-affected and less-affected arm) showed strong correlation with FMA, after controlling for cofactors, such as age, sex, time since stroke, sensory deficit, neglect, apraxia or lower extremity function (17). Knowledge is, however, limited regarding how different relevant cofactors might be associated with real-life activity in people with stroke in a multifactor model. Such knowledge is necessary to advance the routine use of technology-based assessment in clinical practice (19–21).The aim of this study was to determine to what degree arm, leg and trunk activity, measured with accelerometers, is associated with sensorimotor impairments and activity limitations as well as clinical and demographic characteristics in individuals with subacute stroke.