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Fatigue in Triathletes

By Benjamin A. Hasan | Jan. 24, 2019, 11:59 a.m. (ET)



“I train regularly for triathlon. Why am I so tired?”


Fatigue occurs in triathletes. Endurance athletes are often driven in many aspects of their lives, including their athletic training and competition. They expect to have more energy than others, not less. Fatigue is not welcome.


Every now and then, the energy is simply not there. “Fatigue” can appear in triathletes as a loss of vigor for training, a change in our heart rate with training and racing, the need for more sleep, loss of motivation for our sport or for other things in life, sleepiness, or simply feeling drained or down all day.


My medical approach for evaluation of fatigue in triathletes is similar to the medical approach to fatigue for I perform for any adult or child. I start by taking a good history that includes focused questions and listening to the specific responses. Often the responses provide clues to the etiology of the fatigue. Is there a sleep issue? Is the athlete feeling ill? Is there significant new home or work stress? Is there a new baby? Are there additional symptoms that indicate a medical illness? Is there blood loss or other suggestions of anemia? Physical examination and additional testing, such as blood work when indicated, provides further data to help determine the cause of fatigue.


Upon completion of my evaluation, I assemble a list of possible causes. In the medical field, we use the term “differential diagnosis” as our name for that list. Fatigue in athletes can be caused by (the differential diagnosis can include):

  1. a virus such as a respiratory infection or intestinal virus
  2. a thyroid problem
  3. insufficient sleep
  4. overtraining
  5. blood-loss anemia (not enough iron in the red blood cells)
  6. anemia from not enough iron in the diet (iron deficiency)
  7. depression

It is, of course, possible to experience more than one of the above conditions. A common and useful method to find a solution is to eliminate potential causes one by one.




Infections can cause a variety of symptoms. It is true that endurance athletes are more prone to virus infections than the non-exercising population. Close contact with others, training in groups, and the grueling training programs of many athletes can lead to the immune system becoming worn down enough to get sick. As with most people, common virus infections such as colds, bronchitis, and gastroenteritis (called the “stomach flu,” although not caused by influenza) are benign conditions and generally run their course, allowing us to recover fully in several days. Fatigue can continue for a few more days in many cases. Washing your hands, being careful with what we put in our mouth (orange slices at the end of a race after they have been handled by other sweaty athletes), covering our mouths when we cough, and avoiding being coughed on or sneezed on can all help prevent these common infections.


Thyroid disease


A simple thyroid blood test can make a diagnosis of an over- or underactive thyroid gland. The thyroid gland is located in the neck. The thyroid hormone it produces helps to set our metabolic pace for most of the body functions. If the thyroid is producing too little thyroid hormone, you may feel slow or tired or lethargic. A slowing of the bowels (constipation), slowing of the heart function, and dry skin can also occur in some people.


Insufficient sleep


There are productive professionals and accomplished athletes performing well with small amounts of sleep. In some circles, this has become a badge of courage. When an athlete is getting six hours of sleep regularly, and their routines have left them feeling worm out and tired, sleep experts explain that adding more sleep should be the first intervention. They even recommend eight hours for someone sleeping seven hours each night when seven is not enough for that person. Although the amount of sleep any of us requires varies greatly, we know that seven or eight hours are required for most adults, especially those training at a high level. Even when sleep is not the only issue contributing to fatigue, adding a bit more can be a major part of the solution.



Triathlon is a sport based on heavy training, years of experience, adding miles, varied routines, volume, persistence, and repetition. For most competitive athletes, there is a fine line between success and fatigue. That balance is the essence of the sport. The cardiac health we gain from training, the sense of accomplishment and personal identity, the opportunity to demonstrate an athletic life and lifestyle, and the physical joy of competition contribute much to our lives. When these routines cause fatigue, it is important to rule out other medical causes and then consider adjusting your training and racing plans accordingly.


Blood loss causing anemia


The medical term “anemia” is defined by a low “hemoglobin” measurement or a low amount of red blood cells. Hemoglobin is a protein with iron at its center. It carries oxygen in the blood and allows circulation of oxygen to our tissues at rest and during sports. Healthy menstruating women can lose enough blood on a regular basis to be anemic. Men and women may lose blood through the urine or through the stool without seeing it. Blood loss can indicate a serious medical condition, including cancer of the intestine, kidney, or bladder. This blood loss is one of the many reasons to see a physician when fatigue becomes a noticeable issue. Anemia and loss of blood can be diagnosed with a few simple tests, including a “CBC” (Complete Blood Count).


Anemia from not enough iron in the diet


Iron is supplied to us through our diet. We ingest significant amounts of iron through green leafy vegetables, red meats and poultry, and dairy products. Many healthy people in the United States, including triathletes, do limit some of these foods. Examples include vegetarians and those with lactose sensitivity from dairy foods. If anemia is present (low blood hemoglobin), then a focus on both the causes and the solution can be straightforward. Iron-deficiency anemia can be successfully treated with oral iron tablets. These tablets can cause the stool to be dark and may contribute to constipation in some people.




If you and your physician feel depression is playing a role in fatigue, then addressing this in detail is very important.


Fatigue is a part of the sport of triathlon. However, when an athlete is fatigued more than expected, and more than what is likely caused simply by participating in a tough sport with a tough regular routine, it is important to see your physician. Primary Care Sports Medicine physicians are specifically trained to handle these and other medical symptoms and injuries common to athletes.


Benjamin A. Hasan, MD, is a team physician for USA Triathlon and practices both Family Medicine and Sports Medicine with the Northwest Community Hospital Medical Group in the Chicago suburbs. He is the Director of the NCH Back and Spine Clinic, has been a Chicago Marathon volunteer physician for 25 years, and has covered over 550 athletic events as a team physician, including the Salt Lake City Olympic Winter Games and eight ITU World Championships for USA Triathlon. He is a 25-year member and regular contributing instructor with the American Medical Society for Sports Medicine, and holds academic appointments at Northwestern University’s Feinberg School of Medicine and the University of Illinois College of Medicine in Chicago.