Edinburgh Napier University

  Background: Accurate physical activity monitoring is important for cardiac patients. Novel activity monitoring devices may enable precise measurement of physical activity. This study aimed to validate Fitbit-Flex against Actigraph accelerometer for monitoring physical activity.
Design: A validation study with a comparative design.
Methods: Cardiac patients and family members participating in community-based exercise programs wore Fitbit-Flex counts and minutes of moderate to vigorous physical activity (MVPA).
Results: Participants (N¼48) comprised 52.1% males, with a mean age of 65.66.9 years and 58.9% had a cardiac diagnosis. Fitbit-Flex and Actigraph were significantly correlated in males, females, total participants and cardiac patients for step counts (r¼.96; r¼.95; r¼.95; r¼.95), though less so for MVPA (r¼.81; r¼.65, r¼.74; r¼.71). As step counts increased the differences between Fitbit-Flex and Actigraph also increased. Fitbit-Flex over-estimated step counts in females (556 steps/day), males (1462 steps/day) and total participants (1038 steps/day) as well as for minutes of MVPA
in females (4 min/day), males (15 min/day) and total participants (10 min/day). Fitbit-Flex had high sensitivity and specificity in classifying participants who achieved the recommended physical activity guidelines.
Conclusion: Fitbit-Flex is accurate in assessing attainment of physical activity guideline recommendations and is useful for monitoring physical activity in cardiac patients. The device does, however, slightly over-estimate step counts and MVPA.