Marathon running leads to a severely compromised immune system, reduced T-cell and natural killer cell activity, and high levels of stress hormones and inflammatory molecules.

“people who just ran a marathon and people who have been training for a marathon and are approaching that Marathon are severely immune compromised the levels of their te- cell function are way below Baseline meaning their inate immune system is not functioning nearly as well as it would if they were to not exercise at all their natural killer cell activity is also greatly diminished these are huge huge reductions in these cells that is in the function of the inate immune system and their stress hormones and their inflammatory molecules such as cyto circulating in their blood are extremely high”