The main benefit of cross-training in a fitness program is its ability to enhance overall fitness by engaging various muscle groups and reducing the risk of injury. By incorporating diverse activities—such as running, swimming, and strength training—individuals improve their cardiovascular endurance, flexibility, and strength. This variety prevents training monotony, keeps the body adaptable, and increases progress. Cross-training also allows for active recovery, ensuring muscle groups receive adequate rest. Overall, it helps maintain enthusiasm for long-term fitness goals.