Article Text

Download PDFPDF
F62 Validation of digital assessment of physical activity in Huntington’s disease: comparing fitbit charge 4 step count with research-grade accelerometers
  1. Elliot Mann1,2,
  2. Cheney JG Drew2,
  3. Monica Busse2,
  4. Emer Doheny3,
  5. Madeleine Lowery3,
  6. on behalf of the DOMINO-HD Consortium
  1. 1School of Biosciences, Cardiff University, Cardiff, UK
  2. 2Centre for Trials Research, Cardiff University, Cardiff, UK
  3. 3School of Electrical and Electronic Engineering, University College Dublin, Dublin, Ireland


Background Physical activity has been implicated in improving symptom management and quality of life in Huntington’s disease (HD). Verifying the role of physical activity in HD requires accurate quantification of exercise metrics.

Aim To assess the reliability and validity of Fitbit® Charge 4 step-count compared to research accelerometers and observer count in HD patients.

Methods 17 manifest HD participants completed two indoor 2-minute walking tests (2MWT) while wearing a Fitbit® charge 4, and an ActiGraph GTX9 on their non-dominant wrist, ActivPAL4™ on both anterior thighs, and ActiGraph GTX9 on both anterior shanks. Steps were manually counted from video recordings of the 2MWTs. Step-counts for devices were obtained from their proprietary software. Intraclass correlation coefficients (ICC) determined Fitbit and observer reliability, whilst Bland-Altman (B-A) analysis demonstrated monitor agreement.

Results Intra-rater reliability of researcher count from repeat trials was excellent (ICC 0.95/n = 17) meanwhile, Fitbit yielded good reliability (ICC 0.81/n = 16). B-A plots displayed greatest agreement between Fitbit and manual count (bias -4.7/SD 36.2). Average monitor count revealed largest consistencies with ActivPAL4 and Fitbit (bias -3.4/SD 37.4) whereas, wrist-worn ActiGraph deviated markedly (bias 4.9/SD 66.9). Motor symptom severity did not influence average Fitbit count although, upper extremity devices occasionally underestimated steps produced.

Conclusions Whilst superior step-count accuracy was seen with devices placed on lower limbs, these data show that Fitbit charge 4 may be a reliable device for monitoring steps in manifest HD.

  • Fitbit Charge 4
  • Step count
  • Validity
  • Reliability
  • Digital assessment

Statistics from

Request Permissions

If you wish to reuse any or all of this article please use the link below which will take you to the Copyright Clearance Center’s RightsLink service. You will be able to get a quick price and instant permission to reuse the content in many different ways.