Introducing the New Sister App dedicated for the gym

13 years ago, I launched Exercise Timer.

What started as a simple timer slowly grew into something much bigger. Over the years, millions of people downloaded it. Today, it has more than 3 million users and has evolved into a mature fitness platform packed with features for interval training, HIIT, running, circuits, and home workouts.

As the user base grew, so did the feedback. Few request appeared again and again:

“Can you add sets, weight and reps logging?”

“Can you add supersets?”

The problem was that gym logging is fundamentally different from interval training. Over the years, I explored multiple designs and prototypes. Features that made sense for weight training cluttered the experience for interval users. The app risked becoming a jack-of-all-trades instead of excelling at what it was originally built for.

After years of hearing the same requests, I realised the right solution wasn’t to force gym features into the interval app.

The right solution was to build a completely new app from the ground up.

That’s how WorkoutStack was born.

Built Specifically for the Gym

WorkoutStack is designed around the needs of gym-goers from day one.

You can create & organize routines. Add exercises, track sets, log weights and reps, build supersets, and manage rest intervals without fighting against a timer-focused interface. On the other hand I wanted to keep all the things I love about Exercise Timer. Like the bold colors, personalised routine icons, offline mode, routine organisation & more.

Works Offline

One lesson I’ve learned after building fitness apps for more than a decade is that reliability matters.

Gym basements, underground parking garages, and crowded fitness centers don’t always have a great internet connection.

That’s why WorkoutStack is designed to work offline.

Your workouts, exercise library, and training data are available when you need them, regardless of signal strength. You shouldn’t have to depend on a network connection to record a set.

This architecture has three major advantages.

• First, it’s incredibly fast. Since the data is stored locally, there’s no waiting for screens, workouts, or exercises to load.
• Second, it enables richer statistics. Because all workout data is available on-device, WorkoutStack can generate more detailed insights and training analysis without relying on a server.
• I can provide a cheaper price to users, since the server costs, although not negligible, do not inflate the price.

A Library of More Than 2,900 Exercises

One of the biggest challenges when building a gym app is creating a useful exercise database.

WorkoutStack launches with more than 2,900 exercises, complete with muscle and equipment information.

Whether you’re using barbells, dumbbells, machines, cables, kettlebells, resistance bands, or specialty equipment, chances are the exercise is already available in the library.

All these exercises can be used for reference, while creating routines & logging workouts.

Understanding Your Training

Logging workouts is useful. Understanding them is even better.

WorkoutStack analyzes your completed exercise sets and calculates muscle distribution across your training. This makes it easier to identify imbalances, understand what muscles you’re emphasizing, and ensure you’re training the way you intend.

Apart from this, you get 100s of different stats to help you analyse your performance. Stats are divided in widgets which you can pick and add to our custom stat dashboard. This allows you to see the analytics that are most important for you personally.

Built With Modern Technology

While most users will never care about the technical details, those decisions help deliver a faster, more reliable app.

WorkoutStack is built entirely in SwiftUI, Apple’s modern framework for creating native iOS apps. This allows me to provide an experience that feels right at home on iPhone, with smooth performance and deep platform integration.

Under the hood, the app uses a local database architecture designed for speed and offline reliability. Your workouts and exercise library are always available, even without an internet connection.

One thing that’s important to me: WorkoutStack is not “vibe coded.”

I use AI as a tool throughout the development process, but AI never has direct access to the codebase and every line of code is reviewed before it becomes part of the app. After 13 years of building Apps, I care deeply about understanding every part of the architecture and maintaining full control over how the product evolves.

AI can accelerate development, but responsibility for the code, architecture, and user experience remains entirely mine.

Excited to see how people use it

Building Exercise Timer taught me a lot over the last 13 years.

Most importantly, it taught me that the best features often come directly from users.

WorkoutStack exists because thousands of people kept asking for particular features. Instead of forcing those features into an app that wasn’t designed for them, I decided to start fresh and build something purpose-built for strength training.

This is only the beginning. I’m excited to see where WorkoutStack goes next, and even more excited to build it alongside the people who use it every day.

As a thank you for being an Exercise Timer user, we’re offering 50% off the WorkoutStack Lifetime plan.

Code: SAVE50PERCENT