← Frederik Smal

Case study · 2026

GymBro Designed. Built. Used every day.

Most fitness apps hide the one number you need inside charts and history. GymBro shows what you did last time and what to do now.

  1. RoleProduct, design and build
  2. StatusSelf-initiated, August 2026. In daily use.
  3. Built withHTML, CSS, JavaScript, PHP, MySQL
Four GymBro screens: body measurements, a finished workout, the monthly report and one exercise.
Flow sketch: Insights show the signal first, and adding a set keeps the context.Flow sketch: the body weight card, its trend, and adding a new reading.Flow sketch: choose a period, see the summary first, then the best progress.The summary after a finished workout.

The problem

Between sets you need one answer, not a chart.

Every exercise opens with the previous weight, reps and date, then suggests maintaining, adding reps or adding weight. Single-arm exercises track each side. Four views cover body measurements, completed workouts, monthly insights and exercise history.

DecisionShow one instruction instead of a chart.

The build

No framework. No build step.

Three flows on paper first, then plain HTML, CSS and JavaScript, with PHP and MySQL on shared hosting, and an offline queue for dropped connections. Claude helped scaffold screens and debug; I tested the flows and checked the data myself.

AI’s role

A coach that reads the data, not a calculator.

Every number on screen is calculated, not generated. Every few weeks I give Claude my goal and the full dataset and ask for changes to the program. I review every suggestion before anything changes.

DecisionAI proposes. I decide.