Marathon training: why hot baths might help you run faster

For decades, elite runners have travelled the world to train at high altitude. When oxygen levels in the air are low, the body responds by producing more red blood cells – the cells responsible for carrying oxygen around the body. When athletes return to sea level, this greater oxygen-carrying capacity can enhance endurance performance.

But altitude training comes at a cost. It requires time away, financial investment and long-haul travel. For the vast majority of runners lining up at this year’s London Marathon...