Do Challenging Training Sessions Suppress The Immune System?

December 6, 2019

Are you more likely to get sick after a difficult training session?

If so, are there any ways to help avoid getting sick?

After a stressful bout of exercise, research suggests that the immune system is temporarily suppressed for a period of hours (i.e., immunosuppression).

This temporary suppression can increase the potential of acquiring an infection in the hours following a stressful bout of exercise (e.g., upper respiratory tract infection [URTI]).

This seems to be partially related to elevations in blood plasma levels of cortisol. Cortisol can interfere directly with certain immune cells’ functions (2,3)

For a period of hours after training, decreases in circulating immune cells, salivary immunoglobulin levels, and nasal immune cell content have been shown to occur (1,3).

Since challenging training sessions are necessary to maximize progress over time, what can be done to help avoid acquiring an illness after a productive overloading session?

1 – Appropriate energy and macronutrient intake can help support restoration of a more ideal hormonal milieu that can support immune function.

2 – Avoiding crowded places and environments in the “open window” of ~8 hours after training where exposure to pathogens is potentially higher can reduce the likelihood of getting sick (e.g., mall, grocery store, etc.).

3 – Taking a shower after a training session and practicing good hygiene can decrease the exposure to a pathogen in the hours following training that may be present on the body or clothing.

4 – High quality and sufficient quantity of sleep in the hours following can support immunity.

Interestingly, individuals who regularly perform moderate amounts of exercise tend to acquire less infections compared to sedentary individuals, on average. So, this isn’t to say that regular exercise negatively affects immune function.

So, in general, regular exercise appears to support immunity. Yet, it’s important to be aware that after particularly hard sessions the risk for acquiring an illness is probably higher for ~8 hours after the session. Being mindful of the strategies described above and using them intelligently can reduce the likelihood of getting sick.

Staying healthy can improve the probability of more regular productive training over broad time; and thus better results.


  1. Faculty of Health Sciences and Medicine, Bond University, Robina, Queensland, Australia.
  2. Int J Sports Med. 1996 Nov;17(8):597-603.
  3. Institute of Medicine (US) Committee on Military Nutrition Research. Military Strategies for Sustainment of Nutrition and Immune Function in the Field. Washington (DC): National Academies Press (US); 1999. 17, Exercise, Infection, and Immunity: Practical Applications.!po=0.434783