The concept of progressive overload is crucial in strength training, as it involves gradually increasing the amount of weight or resistance during workouts. This principle forces the body to adapt, enhancing muscle strength and endurance over time. Without progressive overload, muscles can plateau, hindering progress and limiting overall fitness gains. It also encourages continual adaptation, which is essential for building muscle mass and increasing strength. By systematically overloading different muscle groups, individuals can experience ongoing improvements in their fitness levels.