Wearables, Physical Activity, and Exercise Testing in Liver Disease

Abstract

Physical inactivity is a major cause of deterioration in all forms of advanced liver disease. It is especially important as a driver of the components of the metabolic syndrome, with nonalcoholic fatty liver disease rapidly becoming the dominant cause of liver-related death worldwide. Growing realization of the health benefits of moderate-to-vigorous physical activity has captured the interest of persons who desire to improve their health, including those at risk for chronic liver injury. They are increasingly adopting wearable activity trackers to measure the activity that they seek to improve. Improved physical activity is the key lifestyle behavior that can improve cardiorespiratory fitness, which is most accurately measured with cardiopulmonary exercise testing (CPET). CPET is showing promise to identify risk and predict outcomes in transplant hepatology. Team effort among engaged patients, social support networks, and clinicians supported by web-based connectivity is needed to fully exploit the benefits of physical activity tracking.

Fig. 1

Physical activity trackers. The development, appearance, and functionality of various classes of physical activity trackers are illustrated. Details and references are provided in the Activity Measurements section of the accompanying text.

Fig. 2

Number of daily minutes spent at each activity category according to three measuring methods. The minutes spent at the lowest intensity (i.e., sedentary) are shown as percentage of 1,440 minutes/day. Cadence categories: sedentary 0–19 steps/min, very light 20–39, light 40–79, moderate 80–130, and vigorous > 130. Heart rate reserve (HRR) categories: very light activity < 30%, light 30–39, moderate 40–59, vigorous 60–89, and maximal 90. Fitbit metabolic equivalent (MET) categories: sedentary < 1.5 METs, lightly active 1.5–3, fairly active 3–6 for ≥ 10 minutes, and very active ≥ 6 for ≥ 10 minutes. Comparison was performed combining very light plus light activities in the same category for cadence, and vigorous plus maximal for HRR.