Grivas 2025, physiology and psychology of negative splits

Frontiers in Physiology review of marathon pacing arguing that even or slightly negative splits are optimal for most runners. Mechanisms cited: conservative early pacing spares muscle glycogen by drawing more energy from fat oxidation, limits early lactate accumulation, attenuates cardiovascular drift and reduces heat build-up, all delaying late-race fatigue. Notes elite marathoners often run slight negative splits while most recreational runners run positive splits from an unsustainable start.