What makes implementation intentions (in)effective for physical activity among older adults?

Abstract

For most populations, implementation intentions (IIs) facilitate physical activity (PA). However, for older adults, previous studies found mixed evidence for the effectiveness of this behaviour change technique. To examine which characteristics of IIs predict successful enactment, the content of older participants' IIs formed within a self-regulatory intervention to prompt PA was analysed. A sample of N = 126 German speaking adults aged 64 and older formed up to six IIs for PA and reported their enactment 5 weeks later. Controlling for age and sex, multilevel models tested associations between characteristics of IIs (e.g., chronological rank of II, hetero- and homogeneity, specificity, presence of certain cues) and enactment. Significantly related to enactment were: the chronological rank of an II (first IIs superior to last IIs), greater heterogeneity in activities, greater specificity of when-cues, and greater use of pre-existing routines. Participants were more likely to enact their IIs 5 weeks later if they planned different (heterogeneous) activities, created IIs with more specific when-cues (e.g., on Monday at 9 am), and in particular a routine (e.g., after breakfast). They also enacted the first three IIs (chronological rank of II) more often than the last three IIs. Future experimental studies should test whether providing instructions to create IIs based on the above significant characteristics lead to more effective health behaviour change among older adults.