Acceptability and Usability of a Theory-Driven Intervention via Email to Promote Physical Activity in Women Who Are Overweight or Obese: Substudy Within a Randomized Controlled Trial

BACKGROUND: Insufficient physical activity (PA) and excess weight increase illness risk for women. Face-to-face interventions can increase PA levels; however, they are often inaccessible. With growing interest in digital interventions, a Self-Determination Theory (SDT)–driven intervention was developed and delivered via email to promote PA in women who were insufficiently active and overweight or obese. OBJECTIVE: This substudy explores users’ perspectives about the acceptability and usability of the intervention, which was coupled with a wearable activity monitor and PA recommendations. METHODS: A 3-arm, parallel group, randomized controlled trial (unblinded) was conducted in Ontario, Canada. Recruitment occurred from September 2018 to March 2019 via advertising through social media, web-based boards, and posters in publicly accessible areas. In total, 47 women with a BMI of ≥25 kg/m(2) who were not meeting the Canadian PA guidelines were randomly assigned to 1 of 3 arms (arm 1: n=15, 32%; arm 2: n=16, 34%; arm 3: n=16, 34%). This substudy focused on the 15 participants allocated to the main intervention arm. Participants received an automated intervention consisting of (1) 6 weekly emails, (2) a Polar Electro Inc A300 activity monitor (with access to the Polar Flow website and companion smartphone app), and (3) a copy of the Canadian PA guidelines for adults. Emails were developed using SDT and designed to enhance autonomous motivation by fostering the psychological needs of competence, autonomy, and relatedness. Well-established motivational and behavior change techniques were embedded in the emails to promote needs satisfaction. After the intervention (ie, 7 weeks after randomization), participants were invited to complete a web-based acceptability and usability survey containing open-ended and closed-ended questions; responses were analyzed using descriptive and content analyses, respectively. RESULTS: The analyses included data from 93% (14/15) of the women (age: mean 33.4, SD 7.5; range 24-44 years; BMI: mean 31.3, SD 5.8 kg/m(2); range 25-40.5 kg/m(2)) who received the main intervention and completed the postintervention survey. Open-ended responses indicated that participants were generally satisfied with the intervention and appreciated that emails prompted self-reflection, kept them on track and accountable, provided informational support, and were nonpressuring. Furthermore, they suggested that the monitor was “enjoyable” and “helpful”; quantitative data corroborated this, as 71% (10/14) said that the monitor was “very valuable/absolutely valuable,” 71% (10/14) would “very probably/definitely” still use one, and 86% (12/14) wore it for ≥5 days per week for ≥8 hours per day and checked it “occasionally/frequently/very frequently.” Potential threats to acceptability included “long” and “text-heavy” emails; lack of personal contact; and cumbersome, unaesthetic monitors. CONCLUSIONS: Results suggest that this SDT-driven, email-delivered intervention may be an acceptable low-contact approach to promote PA in women who are overweight or obese and insufficiently active; however, improvements are warranted and studies ascertaining its effectiveness are needed. TRIAL REGISTRATION: ClinicalTrials.gov NCT03601663; http://clinicaltrials.gov/ct2/show/NCT03601663 INTERNATIONAL REGISTERED REPORT IDENTIFIER (IRRID): RR2-10.1177/20552076221093134