7.1-Effects of Extreme Environments on Infections & Immunity

• What do we mean by environmental extremes?

  Conditions that cause extreme environmental stress
• What are the types of extreme environmental stress experienced by athletes?

  • High altitude (up to 5000 m)
  • Hypothermia (core temperature <35°C)
  • Exertional heat illness (core temperatures >41°C)
• What are the types of moderate environmental stress experienced by athletes?

  • Moderate altitude or hypoxia (up to ~2500 m)
  • Peripheral cooling
  • Exertional hyperthermia (core temperature >39.5°C)
• What should you be able to explain by the end of the session?

  Links between environmental extremes and immune function
• What is the effect of high altitude on infection in athletes?

  It can negatively impact immune function
• What is the effect of cold exposure on infection in athletes?

  It can negatively impact immune function
• What is the effect of extreme heat exposure on infection in athletes?

  It can negatively impact immune function
• What was the sample size of elite endurance athletes in the study by Bailey et al.?

  24 elite endurance athletes
• What was the altitude range for the training camps in the study?

  ~1500-2000 m
• What symptoms were reported by athletes during the training camps?

  Cold symptoms, cough, fever, diarrhea

  
• What is a significant risk factor for infection in athletes according to Svendsen et al.?

  Long haul air travel
• How much does air travel increase the risk of infection?

  5 times
• What is the effect of competition on the risk of infection?

  It increases the risk by 3 times
• What is the effect of large changes in training load on infection risk?

  It increases the risk by ~16%
• What are the types of T cells and their functions?

  • Helper T-cells (60-70%): Control immune responses
  • Cytotoxic T-cells (30-40%): Kill virus-infected cells
• What happens to T cell proliferation after a long-haul flight?

  It is lower in the days after
• What was the altitude simulated in the hypobaric hypoxic chamber study?

  8000 ft (2438 m)
• What was the mean sleeping time in the hypobaric hypoxic chamber study?

  2.4±0.85 hours
• What immune cell functions are affected by acute and chronic hypoxia?

  Lymphocyte functions are affected
• What happens to CD4+ cells at high altitude?

  They are lowered
• What is the effect of altitude on NK cells?

  Numbers of NK cells increase
• Which T cell responses are affected by high altitude?

  Th1 responses are affected, not Th2
• What happens to mitogen-stimulated T cell proliferation at high altitude?

  It decreases
• What is the effect of acute altitude exposure on T cell immune responses?

  They are lower after exposure
• What is the effect of hypoxic-exercise on immune functions?

  It enhances Type 1 cytokines response
• What is the effect of intermittent hypoxic training on immune cell numbers?

  It doesn’t seem to affect immune cell numbers
• What are the findings regarding self-reported respiratory illness in athletes at high altitude?

  • Increased self-reported respiratory illness
  • Possible overlap with acute mountain sickness symptoms
  • Live-high, train-high methods decrease immune function
• What is the common belief about cold exposure and respiratory illness?

  Breathing cold air causes the common cold
• What is the relationship between hypothermia and common cold symptoms?

  Hypothermia is not associated with increased symptoms
• What effect does peripheral cooling of the nose have?

  It can increase common cold symptoms
• What was the average temperature preceding symptoms in the study by Mäkinen et al.?

  -3.7 ± 10.6°C
• What is the effect of a 1°C fall in temperature on URTI risk?

  It increases the risk by 4%
• What is the effect of a fall in absolute humidity on URTI risk?

  It increases the risk by 10%
• How many episodes of URTI were diagnosed in the study?

  595 episodes
• How many episodes of LRTI were diagnosed in the study?

  87 episodes
• What is associated with non-infectious cough symptoms?

  Airway inflammation
• What is the common belief about cooling of the skin?

  It causes the common cold
• What is controversial regarding the common cold?

  Evidence supporting skin cooling is controversial
• How does hypothermia relate to common cold symptoms?

  It is not associated with increased symptoms
• What effect does breathing cold air have on common cold symptoms?

  It may increase common cold symptoms