The principle of progressive overload involves gradually increasing training intensity to induce muscle adaptation. This is essential for continued gains in both strength and hypertrophy. Strength refers to maximizing the amount of weight lifted, generally measured by a one-rep max, focusing on performance rather than muscle size. In contrast, hypertrophy is the increase in muscle size achieved primarily through myofibrillar hypertrophy, where the number of myofibrils increases, leading to larger muscle fibers and overall muscle thickness. While hypertrophy training aims to change muscle structure, the goal is not to lift the heaviest weights but to grow larger muscles. Adaptive responses to training include not only hypertrophy but also neural adaptations, which enhance strength. To effectively utilize progressive overload, one must manipulate training variables like intensity, volume, and frequency to meet the specific demands of either strength or hypertrophy training, understanding that the required stimulus becomes greater as the body adapts over time.