Training variability and threshold density: a conceptual comparison of East African and Norwegian endurance training systems

East African and Norwegian endurance training systems have both produced world-class distance runners, despite substantial differences in how training is organized, regulated, and executed. East African training is commonly characterized by group-based execution, variable pacing, fartlek-style sessions, and internally regulated intensity, often within altitude-associated environments. In contrast, the Norwegian model emphasizes threshold-density training, lactate-guided intensity control, struct