Background: Consumer and research activity monitors have become popular because of their ability to quantify
energy expenditure (EE) in free-living conditions. However, the accuracy of activity trackers in determining EE in
people with Huntington’s Disease (HD) is unknown.
Research question:
Can the ActiGraph wGT3X-B or the Fitbit Charge 4 accurately measure energy expenditure during physical
activity, in people with HD compared to Indirect Calorimetry (IC) (Medisoft Ergo Card)?
Methods: We conducted a cross-sectional, observational study with fourteen participants with mild-moderate HD
(mean age 55.7 ± 11.4 years). All participants wore an ActiGraph and Fitbit during an incremental test, running
on a treadmill at 3.2 km/h and 5.2 km/h for three minutes at each speed. We analysed and compared the accuracy of EE estimates obtained by Fitbit and ActiGraph against the EE estimates obtained by a metabolic cart,
using with Intra-class correlation (ICC), Bland-Altman analysis and correlation tests.
Results: A significant correlation and a moderate reliability was found between ActiGraph and IC for the incremental test (r = 0.667)(ICC=0.633). There was a significant correlation between Fitbit and IC during the incremental test (r = 0.701), but the reliability was poor at all tested speeds in the treadmill walk. Fitbit
significantly overestimated EE, and ActiGraph underestimated EE compared to IC, but ActiGraph estimates were
more accurate than Fitbit in all tests.
Significance: Compared to IC, Fitbit Charge 4 and ActiGraph wGT3X-BT have reduced accuracy in estimating EE
at slower walking speeds. These findings highlight the need for population-specific algorithms and validation of
activity trackers.
