%0 Journal Article
%@ 1438-8871
%I JMIR Publications
%V 26
%N 
%P e56676
%T Association of Smartwatch-Based Heart Rate and Physical Activity With Cardiorespiratory Fitness Measures in the Community: Cohort Study
%A Zhang,Yuankai
%A Wang,Xuzhi
%A Pathiravasan,Chathurangi H
%A Spartano,Nicole L
%A Lin,Honghuang
%A Borrelli,Belinda
%A Benjamin,Emelia J
%A McManus,David D
%A Larson,Martin G
%A Vasan,Ramachandran S
%A Shah,Ravi V
%A Lewis,Gregory D
%A Liu,Chunyu
%A Murabito,Joanne M
%A Nayor,Matthew
%+ Sections of Cardiology and Preventive Medicine and Epidemiology, Department of Medicine, Boston University Chobanian & Avedisian School of Medicine, 72 E Concord St, Suite L-516, Boston, MA, 02118, United States, 1 617 638 8771, mnayor@bu.edu
%K mobile health
%K smartwatch
%K heart rate
%K physical activity
%K cardiorespiratory fitness
%K cardiopulmonary exercise testing
%D 2024
%7 13.6.2024
%9 Original Paper
%J J Med Internet Res
%G English
%X Background: Resting heart rate (HR) and routine physical activity are associated with cardiorespiratory fitness levels. Commercial smartwatches permit remote HR monitoring and step count recording in real-world settings over long periods of time, but the relationship between smartwatch-measured HR and daily steps to cardiorespiratory fitness remains incompletely characterized in the community. Objective: This study aimed to examine the association of nonactive HR and daily steps measured by a smartwatch with a multidimensional fitness assessment via cardiopulmonary exercise testing (CPET) among participants in the electronic Framingham Heart Study. Methods: Electronic Framingham Heart Study participants were enrolled in a research examination (2016-2019) and provided with a study smartwatch that collected longitudinal HR and physical activity data for up to 3 years. At the same examination, the participants underwent CPET on a cycle ergometer. Multivariable linear models were used to test the association of CPET indices with nonactive HR and daily steps from the smartwatch. Results: We included 662 participants (mean age 53, SD 9 years; n=391, 59% women, n=599, 91% White; mean nonactive HR 73, SD 6 beats per minute) with a median of 1836 (IQR 889-3559) HR records and a median of 128 (IQR 65-227) watch-wearing days for each individual. In multivariable-adjusted models, lower nonactive HR and higher daily steps were associated with higher peak oxygen uptake (VO2), % predicted peak VO2, and VO2 at the ventilatory anaerobic threshold, with false discovery rate (FDR)–adjusted P values <.001 for all. Reductions of 2.4 beats per minute in nonactive HR, or increases of nearly 1000 daily steps, corresponded to a 1.3 mL/kg/min higher peak VO2. In addition, ventilatory efficiency (VE/VCO2; FDR-adjusted P=.009), % predicted maximum HR (FDR-adjusted P<.001), and systolic blood pressure-to-workload slope (FDR-adjusted P=.01) were associated with nonactive HR but not associated with daily steps. Conclusions: Our findings suggest that smartwatch-based assessments are associated with a broad array of cardiorespiratory fitness responses in the community, including measures of global fitness (peak VO2), ventilatory efficiency, and blood pressure response to exercise. Metrics captured by wearable devices offer a valuable opportunity to use extensive data on health factors and behaviors to provide a window into individual cardiovascular fitness levels. 
%M 38870519
%R 10.2196/56676
%U https://www.jmir.org/2024/1/e56676
%U https://doi.org/10.2196/56676
%U http://www.ncbi.nlm.nih.gov/pubmed/38870519