Workout diary mobile app

We coach a growing community of amateur athletes, and right now everyone logs their training in a mess of notes, spreadsheets and screenshots. People forget what weight they lifted last week, skip sessions because nothing nudges them, and can never see whether they are actually getting stronger. We want a mobile app that turns training into something a person opens every day without effort, so that keeping a diary feels lighter than not keeping one.

The app should let a user follow a plan built from exercises, log each set as they go, and watch their progress build over time. We need sensible reminders that respect the user's schedule rather than nagging, and clear charts that answer one question at a glance: am I moving forward. History has to be easy to browse, editing a past entry must be quick, and the whole thing should work offline in a gym with bad signal and sync later.

We are open to your view on the stack, but we care about a calm, fast interface far more than about feature count. Please share relevant apps you have shipped, how you would model plans and exercises, and how you would keep the daily logging flow down to a few taps. Design that a tired person can use after a hard set is the real deliverable here.