In the vocabulary of Periodization, Junk Miles refer to training volume that lacks a specific physiological objective. These are the miles accumulated in the “gray zone”—too fast to qualify as true Active Recovery or Zone 2 base building, yet too slow to trigger the adaptations associated with threshold or interval training. While they contribute to an athlete’s total weekly volume, junk miles often provide a diminishing return on investment, creating unnecessary residual fatigue without the high-end performance gains of a structured session.
The debate surrounding junk miles centers on the “Volume vs. Intensity” conflict. For the time-crunched athlete, every mile must have a mission. Accumulating “empty” volume can lead to a plateau in aerobic capacity and increase the risk of overtraining. However, in the context of Ultra Endurance preparation, some argue that “time on feet” or “saddle time”—even at an undefined intensity—is necessary for toughening the musculoskeletal system. The challenge for the modern athlete is to distinguish between a purposeful base building ride and a session of junk miles that serves the ego’s mileage target rather than the Training Stress Balance (TSB).
