Directly-measured physical activity is an important outcome in COPD. Sensitive motion detectors worn on the body can be useful to this end. However, the optimal location for wearing these devices remains to be determined. Our study evaluated activity monitoring from three locations: the wrist, ankle, and waist.
COPD patients participating in pulmonary rehabilitation exercise training were studied. Their physical activity was directly observed and recorded in 24 5-minute epochs over 2 hours of exercise. Estimated energy expenditure (EEE, in Kcal) was calculated, based on the type and intensity of this exercise. Simultaneous recordings of physical activity from Omni-directional accelerometers worn at the wrist, ankle and waist were also obtained during exercise. EEE from directly-observed data and the 3 devices were compared using t-tests and regression techniques.
Ten patients (7 female) were studied; their mean age was 68 ± 6 years and FEV1 was 46± 16%. Study patients spent 13% of exercise time using a cycle ergometer, 24% in calisthenics, 26% in treadmill/walking and 36% resting. The directly-observed total EEE was 283 ± 64 Kcal; in comparison, the EEE from the wrist was 253 ± 70 Kcal, p. = 0.03; ankle 304 ± 80, p. = 0.15; and waist 203 ± 62, p. < 0.0001). In stepwise forward regression, output from all three devices significantly contributed to the model predicting observed EEE (R2 = 0.48, p. < 0.0001). Calisthenics and bicycle EEE correlated best with output from the device worn on the wrist, while treadmill EEE correlated best with output from device worn at the waist.
The location of the activity monitor (waist, ankle, wrist) influences estimations of energy expenditure in exercising COPD patients. Simultaneous input from more than one location may provide additional information.
The optimal site(s) for activity monitoring in COPD patients remains to be determined.
Mandeep Kumar, No Financial Disclosure Information; No Product/Research Disclosure Information