What specific protocols or methods have been successful in utilizing indoor training to build cycling endurance, and how do these methods differ from traditional outdoor training in terms of effectiveness in achieving specific performance goals such as increasing functional threshold power or enhancing lactate clearance. Are there any advantages to combining indoor training with high-intensity interval training, and how can this best be integrated into a comprehensive training plan to maximize cycling endurance. How do indoor training tools such as virtual reality, Zwift, and TrainerRoad impact the mental and physical components of cycling endurance, and are there any benefits to incorporating strength training into an indoor cycling routine to improve overall cycling performance.