Plank challenge BeStronger is a free Android app developed by BeStronger that offers an effective exercise plan to strengthen your core muscles. The app provides a 21-day challenge to help users improve their endurance to hold a plank position for up to 5 minutes. If you think that's too easy, the app also allows users to create their own challenge, with more than 20 types of planks to choose from.

The app comes with various features, including daily reminders, motivation levels, statuses, quick stats, and history. The standard plank challenge program is designed for three weeks and provides users with a systematic approach to achieve their fitness goals. The app also offers a history section where users can track their progress and see how they've improved over time.

Plank challenge BeStronger is a great way to challenge yourself, stay motivated, and improve your overall fitness. Its user-friendly interface and customizable features make it an excellent companion for anyone looking to strengthen their core muscles and achieve their fitness goals.