How long is too long? Selecting physical activity duration for acute studies involving people with schizophrenia


Background: When determining the duration of an acute bout of physical activity (PA) in an experiment, it is important for researchers to consider associations between duration and the target outcome, as well as how amenable participants will be to enrolling, and whether they will be capable of completing the study. Researchers must strike a suitable balance when working with populations that are commonly inactive, such as people with schizophrenia. Conceptually, a participant’s task self-efficacy might indicate their willingness to participate in a study and their confidence in completing a PA protocol. To inform a future protocol, this study examined the self-efficacy of individuals with schizophrenia to complete PA bouts of differing durations. Methods: A secondary analysis on reliability data from a Health Action Process Approach inventory for PA in schizophrenia (n=26) was performed. Task self-efficacy was measured using 6-items. Participants rated how confident they were in their physical ability to do 10, 20, 30, 40, 50, and 60 minutes of at least moderate-intensity PA in one session without stopping on a 7-point scale (1=not confident at all; 4=neutral; 7=completely confident). Five planned, Bonferroni corrected (α=0.01), paired t-tests compared responses from 10 to 20 minutes, 20 to 30 minutes, and so forth. Results: Task self-efficacy was highest for 10 (M=6.08, SD=1.8) and 20 minute (M=6.08, SD=1.7) durations. Significant differences arose between 20 and 30 minutes t(25)=3.11, p=.005, and 30 and 40 minutes, t(25)=3.93, p=.001. No other significant differences emerged. Conclusion: Sample size was small; however, significant differences emerged between 20 and 30 minutes with a corrected α level. Participants were equally confident in completing 10 or 20 minute PA protocols, however, protocols lasting longer than 20 minutes may be difficult to recruit for. Researchers can use this information to help maximize recruitment and completion when designing acute PA protocols. 

Acknowledgments: This study was supported by a Canadian Institutes of Health Research (CIHR) operating grant #MOP-115709.