Muscular Judaism is a concept that combines religion and physical fitness. It says that being religious and strong are not separate things that don't have anything to do with each other, but they actually work together.
Imagine that you love playing with toys, but sometimes you have to stop playing and eat your vegetables so that you have energy to keep playing. In the same way, being strong and fit can help you be healthier and have more energy to do the things you love, including religious activities.
Some people who follow Muscular Judaism believe that exercising and being strong helps them connect with God and be more disciplined in their religious practices. They might do exercises like weightlifting or running to help them feel closer to their faith.
So, Muscular Judaism is about finding a balance between taking care of your physical health and your spiritual health. By being strong and fit, you can feel better and more connected to your religion.