What are the most effective ways to structure a winter training program on a standard indoor trainer to maximize gains in power output, endurance, and overall cycling fitness, and how can a rider use data and feedback from the trainer to inform and adjust their training plan to achieve specific goals, such as completing a long-distance tour like the TransAmerica Trail, and what are the key differences in training approach between using a standard indoor trainer versus more advanced smart trainers or virtual training platforms, and how can a rider use a standard indoor trainer to simulate the demands of a long tour, including variable terrain, changing weather conditions, and recovery days, and what are the benefits of incorporating strength training, yoga, or other cross-training activities into a winter training program on a standard indoor trainer, and how can a rider balance the need for intense interval training with the need for recovery and injury prevention on a standard indoor trainer, and what are the most effective ways to stay motivated and engaged during long periods of indoor training on a standard trainer.