Oxygen cost of walking, physical activity, and sedentary behaviours in rheumatoid arthritis.

OBJECTIVES: To evaluate the oxygen cost of gait and measure physical activity profiles, including time spent sedentary, in people with rheumatoid arthritis (RA) and matched controls.
METHOD: We recruited 19 people with RA and 19 controls matched for age, sex, and body mass index (BMI). Demographic details and clinical characteristics of the RA population were recorded. Oxygen uptake per metre walked (oxygen cost) was measured in the laboratory using a portable gas analyser. Activity profiles including the number of steps per day, time spent sedentary (sitting or lying down), and intensity of walking were recorded over 5 days using an activity monitor, from which physical activity was classified by intensity categories. Levels of pain, fatigue, anxiety, and depression were recorded.
RESULTS: People with RA walked with a slower self-selected gait speed (p < 0.001) than controls but there was no difference in the oxygen cost of walking (p = 0.992) between the groups. People with RA took fewer steps (p < 0.001), had increased sedentary time (p = 0.029) and lower time walking at cadences commensurate with moderate to vigorous physical activity (MVPA) compared to controls (p < 0.001). Pain, fatigue, and depression were higher in the RA group (all p < 0.001).
CONCLUSIONS: The oxygen cost of walking in this cohort of people with RA was similar to that of matched controls but there was an increase in time spent sedentary and a reduction in time spent at cadences commensurate with MVPA. Clinical symptoms such as depression, pain, and fatigue may explain the changes in activity/sedentary behaviours in people with RA and require further investigation.