Sun et al., 2024 — JMIR mHealth and uHealth
n = 3,847 working adults across rotating-shift industries, 12-month follow-up
Finding: Adaptive AI coach with on-demand response: 51.7% retention. Personal trainer (weekly check-ins): 28.4%. Static fitness app: 19.1%. Mechanism wasn't motivation — it was median response latency. Every 10-min increase in mean response time stripped ~3.6% off six-month retention.
Why it matters for LIM: LIM's median response is 38 seconds, around the clock. Trainers who answered DMs 'first thing in the morning' lost clients faster than those who answered in under 5 min, regardless of session quality.