What are the specific benefits of using dumb trainers for multi-sport athletes, particularly in terms of their impact on power development, endurance, and overall performance? Are dumb trainers more beneficial for certain sports or disciplines, such as cycling or running, compared to others like swimming or rowing? How do dumb trainers compare to smart trainers in terms of their ability to provide a realistic and engaging workout experience, and do the benefits of dumb trainers outweigh their limitations in this regard? Are there any specific training protocols or workouts that are particularly well-suited for dumb trainers, and how can athletes best incorporate them into their overall training plan? What role do dumb trainers play in the context of periodized training, and can they be used effectively during different phases of training, such as base building or intense interval training? Can dumb trainers be used to improve specific skills or techniques, such as pedaling efficiency or running form, and if so, how can athletes best utilize them for this purpose?