mHealth-Based Just-in-Time Adaptive Intervention to Improve the Physical Activity Levels of Individuals With Spinal Cord Injury: Protocol for a Randomized Controlled Trial

Abstract

Background: The lack of regular physical activity (PA) in individuals with spinal cord injury (SCI) in the United States is an ongoing health crisis. Regular PA and exercise-based interventions have been linked with improved outcomes and healthier lifestyles among those with SCI. Providing people with an accurate estimate of their everyday PA level can promote PA. Furthermore, PA tracking can be combined with mobile health technology such as smartphones and smartwatches to provide a just-in-time adaptive intervention (JITAI) for individuals with SCI as they go about everyday life. A JITAI can prompt an individual to set a PA goal or provide feedback about their PA levels.

Objective: The primary aim of this study is to investigate whether minutes of moderate-intensity PA among individuals with SCI can be increased by integrating a JITAI with a web-based PA intervention (WI) program. The WI program is a 14-week web-based PA program widely recommended for individuals with disabilities. A secondary aim is to investigate the benefit of a JITAI on proximal PA, defined as minutes of moderate-intensity PA within 120 minutes of a PA feedback prompt.

Methods: Individuals with SCI (N=196) will be randomized to a WI arm or a WI+JITAI arm. Within the WI+JITAI arm, a microrandomized trial will be used to randomize participants several times a day to different tailored feedback and PA recommendations. Participants will take part in the 24-week study from their home environment in the community. The study has three phases: (1) baseline, (2) WI program with or without JITAI, and (3) PA sustainability. Participants will provide survey-based information at the initial meeting and at the end of weeks 2, 8, 16, and 24. Participants will be asked to wear a smartwatch every day for ≥12 hours for the duration of the study.

Results: Recruitment and enrollment began in May 2023. Data analysis is expected to be completed within 6 months of finishing participant data collection.

Conclusions: The JITAI has the potential to achieve long-term PA performance by delivering tailored, just-in-time feedback based on the person's actual PA behavior rather than a generic PA recommendation. New insights from this study may guide intervention designers to develop engaging PA interventions for individuals with disability.

Trial registration: ClinicalTrials.gov NCT05317832; https://clinicaltrials.gov/study/NCT05317832.

International registered report identifier (irrid): DERR1-10.2196/57699.

Keywords: community; ecological momentary assessment; just-in-time adaptive intervention; microrandomized trial; mobile health; mobile phone; physical activity; randomized controlled trial; spinal cord injury; wearable sensors.

Figure 1

The proposed intervention builds on the capability, motivation, and opportunity model—a framework for understanding behavior (adapted from Michie et al [31], which is published under Creative Commons Attribution 2.0 International License [37]). The solid arrows represent potential influence between system components. An individual’s capability, motivation, and opportunity interact to generate behavior (eg, physical activity [PA]) that in turn influences these 3 constructs. SCI: spinal cord injury.

Figure 2

Conceptual framework of just-in-time adaptive intervention components including decision points, intervention options, tailoring variables, and decision rules for our proposed study (adapted from Nahum-Shani et al [26], which is published under Creative Commons Attribution Noncommercial International License [39]). SCI: spinal cord injury.

Figure 3

Schedule of reminders delivered over a week on a smartwatch. Participants will receive a daily reminder, except for the day off, on the smartwatch to access the web-based physical activity intervention (WI) program.

Figure 4

Example of feedback and reminders of physical activity. Left: participants will have access to physical activity levels performed over the last 7 days on the smartphone. Right: participants will receive a daily reminder, except for the day off, on the smartwatch to access the web-based physical activity intervention program.

Figure 5

Schedule of reminders, just-in-time adaptive intervention (JITAI) messages, and physical activity recommendations delivered on a smartwatch. (A) Study flow over a week: participants will receive a daily reminder, except for the day off, to access the web-based physical activity intervention (WI) program. Participants will be randomized to receive a standard or tailored physical activity goal, or no goal, for 2 of the days each week. (B) Study flow over a day: participants in the intervention group. Participants will be randomized twice during each day to receive or not receive a JITAI feedback prompt. EMA: ecological momentary assessment; R: randomized.

Figure 6

Example of real-time daily feedback on the smartphone (left) and smartwatch (right). The goal for the day in this example is 27 minutes of moderate-intensity physical activity (PA). This is in addition to having access to PA levels performed over the last 7 days on the smartphone.

Figure 7

Participants will be randomized to a standard goal, tailored goal, or no goal condition within 1 to 2 hours of waking up. Top: goal setting—standard goal. Bottom: goal setting—tailored goal. The “Try again” screen will automatically time out back to the goal screen if the user does not press the “Try again” button in 3 seconds. Messages will be reprompted up to 3 times.

Figure 8

Participants will be randomized to a just-in-time adaptive intervention (JITAI) message or no message twice a day. Left: JITAI message—achieved. Middle: JITAI message—to go. Right: if the user acknowledges the JITAI message, then the user receives a “fortune cookie"–like message on the smartwatch.

Figure 9

Participants will respond to an end-of-day ecological momentary assessment to confirm whether they performed exercises (aerobic, strength, or both).

Figure 10

Flowchart to identify a personalized physical activity (PA) threshold. The new threshold value will allow us to calculate minutes of moderate-intensity PA per day for each participant. AUC: area under the curve; PARA-SCI: Physical Activity Recall Assessment for people with spinal cord injury.