JMIR Publications

ABSTRACT

Background:

The health benefits of physical activity are well-known, but adherence to regular physical activity programs remains a major challenge. Just-in-time adaptive intervention (JITAI) has been proposed as a new intervention design to increase physical activity by delivering an intervention at a time when individuals are more likely to make behavioral changes. However, most studies that have implemented JITAI have used uniform intervention criteria (UIC) across participants rather than personalized intervention criteria (PIC) for the individual.

Objective:

To examine the effectiveness of using JITAI implemented with PIC for increasing physical activity.

Methods:

Participants (n=28) wore a wrist activity monitor for two weeks. In the first week, mean distance moved and sedentary time per hour for each participant were calculated to derive PIC. UIC was obtained from a 2-week preliminary study (n=47) conducted under the same conditions. Participants were divided into two groups which received JITAI to promote physical activity according to either PIC or UIC. In the second week, JITAI prompts were sent every hour if (1) distance moved was shorter and (2) sedentary time was longer than PIC/UIC. Differences in changes in physical activity as a result of implementing interventions according to PIC and UIC were analyzed using multilevel models.

Results:

Both PIC (P<0.001) and UIC (P<0.001) significantly increased physical activity in the first hour after JITAI was received. In that first hour, PIC increased physical activity more than UIC; more calories were burned (P=0.020), more steps were taken (P=0.007) and distance moved was increased (P=0.003). However, over the course of the week, the use of JITAI did not significantly increase physical activity levels.

Conclusions:

Our results suggest that PIC-based JITAI is more effective than UIC-based JITAI, consistent with the idea of a need for precision health approaches. Research is needed to develop effective long-term intervention designs with sustainable effects.