Ultra-endurance events such as marathons, triathlons and Ironman-like competitions have increased significantly in popularity and participation over the last few decades. Many participants stick to strenuous training regimens in preparation for the race day. Some even travel to different corners of the world to compete in races. For a few, the arduous preparation is such a priority that even their family life may take a hit or be sacrificed altogether. Juggling work, life, family and training may be a monumental challenge, but most believe they are accruing a very important health benefit from their involvement in endurance activities. The mainstream belief is that all physical activity is good and enhances one’s health and general wellbeing. The physiological and psychological benefits of a well-constructed daily exercise regimen are well established. Exercise activity performed reasonably is known to boost the immune system and reduce our risk of heart disease, cancer and even neurological decline. But what if participation in these events multiple times a year undermines our immune systems? There may come a point where extreme exercise or physical activity actually becomes a major liability to one’s health. Diehard professional and semi-professional athletes may be doing more harm to their bodies than they realise. And with the support of a cadre of self-proclaimed “coaches” and other so-called “experts”, thousands of people worldwide submit themselves to gruelling training methodologies that slowly corrode their immune systems.Our immune systems are constantly being challenged by a barrage of pathogenic microbes. The robustness of our immune function is influenced by many factors, such as our genetic predisposition, environment, stress levels, diet, lack of sleep, ageing and exercise. Different disease states and modifiable behaviours, such as chemical dependency (eg, smoking, drinking and drug use), also suppress the immune system. It is actually not uncommon for athletes to succumb to upper respiratory tract infections (URTIs), such as the common cold, sinusitis, and tonsillitis, in the days and weeks following a major race. The scientific literature is inundated with reports and studies accounting for such incidences. In fact, studies show a twofold to sixfold increase in risk of getting an URTI in the weeks following marathon and ultramarathon (90-kilometre) races. The risk of contracting some of these illnesses also increases during periods of intense training. When I asked Dr Michael Gleeson, a researcher from Loughborough University who has studied the topic extensively, when exercise actually begins to become a liability, he told me that the immune system begins to be suppressed after an intense, prolonged bout of exercise lasting more than 90 minutes. It would be worth mentioning that for many participants, a marathon can last longer than five hours, and an Ironman potentially could have the duration of up to 17 hours. The causes of immune depression after prolonged exercise are primarily thought to be related to the increase in circulating stress hormones (eg, adrenaline and cortisol). Increased levels of stress hormones depress neutrophils and lymphocytes (B cells), white blood cells known to play a vital role in the integrity of the immune system. The neutrophils in the human body are analogous to the iconic Pac-Man in the famous Eighties video game where the protagonist diligently engulfs every bit of debris, or piece of bacteria, in front of him. Lower levels of these cells make one more susceptible to infections. Prolonged exercise further negatively affects other, more complex mechanisms of immune function. The immune function suppression that takes place following endurance events is reversible. But the problem confronting die-hard fitness enthusiasts is not only the physiological aggression they face during a marathon or Ironman-like competition, but also the undermining of their immune systems that comes from excessive training prior to the race day. Some of the participants in these events may be stuck in a vicious cycle of overexerting their immune systems, which may be taking a hit several times a week from training and finally a knockout on the race day. It seems worthwhile to inquire about the long-term consequences of participating in multiple races and adhering to an arduous training regimen — one that may be stripped of any exercise physiology principles. It would be interesting to make a note of the exercise load ideal for eliciting positive immune responses and promoting general wellbeing. When I asked Dr Gleeson what that exercise regimen would look like, he said that “moderate physical activity [30 to 45 minutes of brisk walking, 5 days per week] would be optimal to promote general health and positive immune adaptations”. This is far removed from a marathon. Moreover, the training methodologies that athletes use to prepare for these events are nowhere near the parameters mentioned by Dr Gleeson. We should not deter people from being active and accruing the benefits of daily physical activity. Rather, we should make people aware of the physiological and psychological benefits of a sensible programme of physical activity in daily life. However, running for four hours or more, as many do in a marathon, or swimming, cycling, and running for ten hours or more, as many do in an Ironman competition, is far from being reasonable and conducive to strengthening the immune system. Instead, such individuals may be systematically undermining the integrity of their systems with a training load that is outrageous. Ricardo Guerra is an Exercise Physiologist. He has a Masters of Science in Sports Physiology from the Liverpool John Moores University. He has worked with several clubs and teams in the Middle East and Europe, including the Egyptian and Qatari national teams.from gulfnews.com