What intensity level is the primary focus of the 80 percent portion in the 80/20 training practice?

In the context of the 80/20 training principle, which suggests that 80% of training volume should be at a lower intensity and 20% at a higher intensity, the primary focus of the 80 percent segment is indeed on lower intensity efforts. This means that during the majority of training sessions, runners should engage in moderate to low-intensity workouts, which emphasize endurance.

The rationale behind this focus is that maintaining a lower intensity allows athletes to build a strong aerobic base, improve their efficiency, and promote recovery while minimizing the risk of injury. These workouts help increase the body's ability to utilize fat as a fuel source, which is crucial for long-distance running. Additionally, lower intensity training enables runners to spend longer amounts of time training, thus enhancing overall endurance without excessive fatigue.

Conversely, high-intensity efforts, while important for building speed and strength, are limited to the 20 percent of training volume to ensure that athletes do not overreach and can recover adequately between these intense sessions. This balanced approach of alternating between low/moderate efforts and higher intensities is vital for achieving optimal performance in endurance sports.