  Physical inactivity is the fourth leading risk factor of mortality globally.
Hence, understanding the physical activity (PA) patterns of youth is essential
to manage and mitigate non-communicable diseases. As digital citizen science
approaches utilizing citizen-owned smartphones to ethically obtain PA big data
can transform PA surveillance, this study aims to understand the frequency of
PA reported by youth using smartphone-deployed retrospective validated surveys
compared to prospective time-triggered mobile ecological momentary assessments
(mEMAs). Using a digital citizen science methodology, this study recruited
youth citizen scientists (N = 808) in 2018 (August 31- December 31) in
Saskatchewan, Canada. Youth citizen scientists (age 13 to 21) reported their PA
using prospective mEMAs and retrospective surveys over an eight-day period. A
significant difference was found in reporting the frequency of PA
retrospectively vs. prospectively via mEMAs (p < 0.000). Ethnicity, parental
education, and strength training were associated with prospective PA frequency;
however, no associations were significant with retrospective PA frequency. With
access to ubiquitous digital devices growing worldwide, and youth having
particularly high digital literacy, digital citizen science for the ethical
surveillance of PA using mEMAs presents a promising approach for the management
and prevention of non-communicable diseases among youth.
