Progressive overload means systematically increasing the demands on your body over time so it's forced to adapt. More weight. More reps. More sets. More range of motion. More time under tension. If you're doing the same thing you did last month, your body has no reason to change. This single principle is the foundation of all training adaptation — whether you're building muscle, getting stronger, improving endurance, or increasing power. Everything else in exercise science is a footnote to this concept.