Google Research

Walking with PACE — Personalized and Automated Coaching Engine

UMAP: 30th ACM Conference on User Modeling, Adaptation and Personalization (2022)


Fitness coaching is effective in helping individuals to develop and maintain healthy lifestyle habits. However, there is a significant shortage of fitness coaches, particularly in low resource communities. Automated coaching assistants may help to improve the accessibility of personalized fitness coaching. Although a variety of automated nudge systems have been developed, few make use of formal behavior science principles and they are limited in their level of personalization. In this work, we introduce a computational framework leveraging the Fogg’s behavioral science model which serves as a personalised and automated coaching engine (PACE).PACE is a rule-based system that infers user state and suggests appropriate text nudges. We compared the effectiveness of PACE to human coaches in a Wizard-of-Oz deployment study with 33 participants over 21 days. Participants were randomized to either a human coach (’human’ arm, n=18) or the PACE framework handled by a human coach (’wizard’ arm, n=15). Coaches and participants interacted via a chat interface. We tracked coach-participant conversations, step counts and qualitative survey feedback. Our findings indicate that the PACE framework strongly emulated human coaching with no significant differences in the overall number of active days (PACE: 85.33% vs human: 92%, [p=NS]) and step count (PACE: 6674 vs human: 6605, [p=NS]) of participants from both groups.The qualitative user feedback suggests that PACE cultivated a coach-like experience, offering barrier resolution, motivation and educational support. As a post-hoc analysis, we annotated the conversation logs from the human coaching arm based on the Fogg framework, and then trained machine learning (ML) models on these data sets to predict the next coach action (AUC 0.73±0.02). This suggests that a ML-driven approach may be a viable alternative to a rule-based system in suggesting personalized nudges. In future, such an ML system could be made increasingly personalized and adaptive based on user behaviors.

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