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Energy Expenditure and Step Count Analysis of the Fitbit Flex Activity Tracker: 1343 Board #18 June 1 900 AM - 1030 AM

Montes, Jeffrey; Navalta, James FACSM

Medicine & Science in Sports & Exercise: May 2017 - Volume 49 - Issue 5S - p 362
doi: 10.1249/01.mss.0000517873.99783.7b
C-31 Free Communication/Poster - Activity Trackers and Smartwatches Thursday, June 1, 2017, 7:30 AM - 12:30 PM Room: Hall F

University of Nevada, Las Vegas, Las Vegas, NV. (Sponsor: Dr. James Navalta, FACSM)


(No relationships reported)

PURPOSE: To investigate energy expenditure (EE) and step count (SC) measurements of the Fitbit Flex (FF) activity tracker during two walking protocols.

METHODS: 49 volunteers (male, N=26, female N=23; age (years) 23.43±6.57; height (m) 1.72±0.11; mass (kg) 76.15±18.46 walked protocol one and 46 (male, N=24, female N=22; age (years) 23.39±6.69; height (m) 1.72±0.11; mass (kg) 76.52±18.73 walked protocol two. 31 (male, N=18, female N=13; age (years) 24.39±7.59; height (m) 1.73±0.10; mass (kg) 77.95±21.52 were used for reliability. Subjects walked for 3 minutes at 1.5, 2.5, and 3.5mph at 0% grade for each protocol. EE and SC values for each speed were compared to a MOXUS respiratory cart and a manual count of steps respectively.

RESULTS: EE@1.5mph (r=0.52, p<0.01; α=0.56; FF:19.43±7.12 Kcal, MOXUS:11.9±3.09 Kcal, p<.01), 2.5mph (r=0.53, p<0.01; α=0.72; FF:25.0±7.3 Kcal, MOXUS:14.43±3.67 Kcal, p<.01), 3.5mph (r=0.61, p<.01; α=0.67; FF:27.2±7.55 Kcal, MOXUS:19.43±4.76 Kcal, p<.01). SC@1.5mph (r=0.4, p<.01; α=0.55; FF:231.05±58.75 steps, Observed:268.95±25.17 steps, p<.01), 2.5mph (r=0.37, p<.01, α=0.50; FF:322.64±42.74 steps, Observed:331.6±21.22 steps, p=.03), 3.5mph (r=0.53, p<.01; α=0.66; FF:366.02±31.35 steps, Observed:379.83±21.58 steps, p<.01).

CONCLUSIONS: Because of the popularity of activity trackers such as the Fitbit Flex, it is important to evaluate their accuracy and consistency. By underestimating steps taken and overestimating the caloric cost associated with it, the Fitbit Flex may be hindering people from reaching the recommended levels of daily exercise that have shown to provide minimum health benefits.

© 2017 American College of Sports Medicine