A simple, real-life movement that improves lower-body strength, balance, and coordination while being easy on your joints.
Relatively simple yet effective exercises are often particularly popular. Step-ups definitely fall into this category, primarily training our glutes and legs. They also burn calories at the same time.
High school athletics were my first exposure to any kind of challenging fitness activity. I distinctly remember experiencing a level of soreness I did not expect or understand, which was confusing.