Overtraining and Sickness in Athletes

By Sheila G. Dean MS, RD, LD

Although it may appear that there is conflicting data about whether exercise can increase or decrease your resistance to illness, i t is certain that physical fatigue, whether caused by exercise or manual work, is a factor affecting susceptibility to illness.

Illness can be devastating to the athlete. Especially when you are, say, only a month or two away from a big event such as the infamous Ironman Triathlon World Championship! Athletes are even known to “go into denial” about their illness until they are so febrile and achy that they can’t even go for a moderate walk. This persistence seems to be a product of the belief that “the harder you train, the better you’ll perform”- or as the saying goes, “no pain, no gain”.

And it’s no wonder. There is a popular belief among those who exercise regularly that they are less susceptible to illnesses such as the common cold. Research backs this belief up. Fit people report getting fewer colds than their inactive peers. For example, the results of two studies of women who exercised five days per week for 45 minutes per session showed that the number of days with upper respiratory tract infection was reduced by nearly half in the group that exercised (1).

At the same time, elite athletes, coaches and sports physicians know all too well about the dangers of overtraining and the risk of getting sick. Famous runners such as Liz McColgan, a top runner in Scotland, Uta Pippig, winner of the 1994 Boston Marathon, and Alberto Salazar, a top runner who trained for the Olympic Marathon in 1984, all blamed overtraining for their poor performances (2). Going to the extreme, Boston Celtics star Reggie Lewis’ death, finally attributed to a chain of events set off by a viral infection, focuses attention on the link of overtraining and illness (3).

So, although it may appear that there is conflicting data about whether exercise can increase or decrease your resistance to illness, it is certain that physical fatigue, whether caused by exercise or manual work, is a factor affecting susceptibility to illness. In a study that examined percentages of runners with upper respiratory tract infections, results suggested that top competitive athletes and those who engaged in very long or intense exercise (such as ultramarathons) were more susceptible to upper respiratory tract infections than less competitive athletes (4). Moreover, the physiological and psychological stress of training and competing at the elite level seems to have a combined effect on susceptibility to illness.

Regardless, the athlete, especially the competitive athlete, must train in order to advance. The concept behind improving athletic performance is called overload training (5). With overload training, athletes take on progressively heavier workloads by increasing either the intensity or the volume of training.

Overloading a muscle leads to a number of physical and chemical changes within the muscle cells, resulting in a heightened work capacity called supercompensation. The repetitive nature of overload training stimulates the nervous system to recruit more muscle fibers to perform the task, resulting in an even stronger contraction. This cyclic process of muscle injury followed by recovery and adaptation leads to improved motor performance.

Similar adaptations occur in aerobic conditioning. Increasing the volume of aerobic exercise stimulates the cardiovascular system to perform at a higher capacity. Cardiac stroke volume rises, vessels that feed blood to exercising muscles increase in number, and muscle enzymes more efficiently convert carbohydrate and fat to energy. As a result, the athlete’s strength and endurance improve.

Identifying the crossover from overload training to overtraining can be tricky. The whole process of short-term muscle injury and regeneration is finely balanced. Too much training stress or too little recovery time after training can lead to overtraining syndrome.

However, even if the athlete is not necessarily overtraining, prolonged endurance exercise can briefly suppress and stress the immune system according to a collection of data summarized and reported by Neiman (2). This increased risk for illness, particularly upper respiratory tract infections, is exacerbated by factors such as lack of sleep, severe mental stress, malnutrition or weight loss. This is in contrast to the “recreational” exerciser who does not appear to have increased risk for infectious illness through more moderate exercise. According to another study (6), if an athlete is already even in early stages of infection, exercise may reduce resistance.

Naturally, an athlete may not want to cut back on his or her training regimen. As a result, other alternatives are experimented with in order to minimize the negative effects of intense exercise on the immune response.

For example, the effect of carbohydrate supplementation, amongst others, was studied by Neiman (7). The results show that during prolonged and intensive exercise, carbohydrate supplementation prevents a rise in stress hormones (cortisol and growth hormone), thereby preventing a weakened immune response and diminishing physiologic stress.

Based on these findings, the following recommendations are made:

·          Maintain proper nutrition.

·          Maintain appropriate body weight.

·          Do not attempt to lose weight too quickly during training since immune system function is suppressed with low caloric intake.

·          Avoid overtraining/chronic fatigue.

·          Get proper sleep regularly.

·          Use supplementation acc ordingly (i.e. carbohydrate and vitamin C supplementation), and preferably under the guidance of a nutrition professional such as the registered dietitian (R.D.)

·          Stay hydrated.

·          Avoid training with sick people.

·          Dress appropriately for the climate you are training in.

·          Manage emotional and mental stress.

·          Consider a flu shot if training the winter season.

References 1. Neiman, DC. Et. al. (1993). Physical activity and immune function in elderly woman. Med. Sci Sports Exerc. 25: 823-831.

2. Nieman, David C. (1998). Immunity in Athletes. Sports Science Exchange. Vol 11 No. 2.

3. Altman, LK, Cooper M. (1994). Virus hurt Lewis heart, autopsy finds. NY Times, February 20, pg. 20.

4. Peters, EM et al. (1983). Ultramarathon Running and Upper Respiratory Tract Infections. South African Medical Journal. Vol 64: 583.

5. Sharkey, B. Physiology of Fitness 3^rd ed. Human Kinetics.

6. Ilback, N. et. al (1984). Modifying effects of exercise on clinical course and biochemical response of the myocardium in influenza and tularemia in mice. Infection and Immunity. 45: 498-504.

7. Nieman, DC. (1998). Influence of carbohydrate on the immune response to intensive, prolonged exercise. Exerc. Immunol.Rev. 4:64-76.

Editor’s Note: SHEILA G. DEAN, MS, RD, LD is a registered and licensed dietitian and exercise physiologist. An educator at heart, Sheila teaches Human Nutrition for nurses at St. Petersburg Junior College. She lectures for groups as young as preschool age to the elderly and retired, authors book reviews and newspaper articles regularly for The St. Petersburg Times and frequently appears on WTSP – CBS – News Channel 10 for interviews. She is also the consulting sports nutritionist and media spokesperson for the Ironman Institute. Sheila is a certified health and fitness instructor with the American College of Sports Medicine.