Validating accelerometry as a measure of physical activity and energy expenditure in chronic stroke

Abstract

Background Accelerometers can objectively measure steps taken per day in individuals without gait deficits, but accelerometers also have the ability to estimate frequency, intensity, and duration of physical activity. However, thresholds to distinguish varying levels of activity intensity using the Actical brand accelerometer are standardized only for the general population and may underestimate intensity in stroke. Objective To derive Actical activity count thresholds specific to stroke disability for use in more accurately gauging time spent at differing activity levels. Methods Men (n=18) and women (n=10) with chronic hemiparetic gait (4±2 years latency, 43% Caucasian, 56% African American, ages of 47–83 yrs, BMI 19 – 48 kg/m2) participated in the study. Actical accelerometers were placed on the non-paretic hip to obtain accelerometry counts during eight activities of varying intensity: 1) watching TV; 2) seated stretching; 3) standing stretching; 4) floor sweeping; 5) stepping in place; 6) over-ground walking; 7) lower speed treadmill walking (1.0 mph at 4% incline); and 8) higher speed treadmill walking (2.0 mph at 4% incline). Simultaneous portable monitoring (Cosmed K4b2) enabled quantification of energy cost for each activity in metabolic equivalents (METs, or oxygen consumption in multiples of resting level). Measurements were obtained for 10 min of standard rest and 5 minutes during each of the eight activities. Results Regression analysis yielded the following new stroke-specific Actical minimum thresholds: 125 counts per minute (cpm) for sedentary/light activity, 667 cpm for light/moderate activity, and 1546 cpm for moderate/vigorous activity. Conclusion Our revised cut-points better reflect activity levels after stroke and suggest significantly lower thresholds relative to those observed for the general population of healthy individuals. We conclude that the standard, commonly applied Actical thresholds are inappropriate for this unique population.

Increased Energy Cost of Mobility in Chronic Stroke

“…Subject characteristics are presented previously [11]. Briefly, the male (n=18) and female (n=10) stroke survivors were older (age: 60.4 ± 1.6 years), obese (BMI: 31.5 ± 1.1 kg/m 2 ; body fat: 37.1 ± 2.4%), and deconditioned (VO2 peak: 19.0 ± 0.98 ml/kg/min).…”

“…The five activities were chosen to capture various lighter (<3.5 METs) intensity mobility-related activities and are described in detail previously [11]. In brief, participants completed each of the following mobility-related activities: 1) stepping in place, 2) floor sweeping, 3) walking around a track, 4) walking on a treadmill at 4% incline at 1 mph (lower intensity), and 5) walking on a treadmill at 4% incline at 2 mph (higher intensity).…”

A review of accelerometer-derived physical activity in the idiopathic inflammatory myopathies

“…Accelerometer use in myositis is still in its infancy, and so it is useful to reflect on how such devices are furthering knowledge in other disease areas. Studies have been able to differentiate the severity of stroke by comparing morning peak of accelerometer-derived physical activity [36, 37]. In multiple sclerosis, disease-specific “count cut-points” were developed, thus allowing intensity of physical activity to be measured [38, 39].…”

Evaluation of a smartwatch-based intervention providing feedback of daily activity within a research-naive stroke ward: a pilot randomised controlled trial

“…A higher activity score can be achieved by either very intense short bursts or very low intensity yet continuous movement. Activity was not summated into standardised thresholds of passive, moderate or vigorous exercise as this has been shown to be inappropriate for individuals with stroke [ 35 ].…”