Heat exhaustion and sports anemia

Heat exhaustion and sports anemia

Mitsutoshi Hayashi

Mitsutoshi Hayashi

Doctor of Medicine, specialist in the Japanese Society of Rehabilitation Medicine, specialist in the Japanese Society of Orthopaedic Surgery, specialist in the Japanese Society of Rheumatology, staff to strengthen JOC, and sports physician certified by the Japan Sports Association

Heat exhaustion and sports anemia

Top-level athletes who continue relatively hard sports are more likely to develop sports anemia.

In the summer season, there are many causes of heat exhaustion, including heat stroke, dehydration, exhaustion, anemia, loss of appetite, and sunburn. Athletic anemia is a particular concern during this period.
Sports anemia is an anemia caused by sports, and it is prone to occur among those who continue playing relatively intense sports. Anemia ma y be caused by sweating (which is particularly common in summer), urine (which had been screened for hematuria), iron deficiency due to the loss of iron in hemoglobin excreted in feces (tarry stool typically seen among long-distance runners), hemolysis (march hemoglobinuria) caused by sports that repeatedly impact the soles such as marathon, volleyball, and basketball, or sports in which the body is repeatedly hit such as Kendo. Other signs include dilution of the blood (increased plasma), that is, spurious anemia during the acute phase of exercise. In growing athletes, iron is used not only to make blood but also to make tissues, such as muscles and bone that make up the body. That is, we can’t get enough of iron. In addition, growing female athletes need special attention because menstrual blood loss may lead to increased anemia.


Symptoms include fatigue, loss of appetite, general fatigue, headache, palpitations and shortness of breath (a sense of going to a high altitude), paleness of palpebral conjunctiva, deformity of the nail, and decreased concentration. These symptoms may lead to poor performance and poor growth.


I, as a doctor of the national team in Japan, have seen approximately 10% of male and 20% of female players with anemia in the medical checkups of members of the national team. Two of 18 male players (11.1%) and 4 of 18 female players (22.2%) had anemia on blood tests. And I think there are many anemic athletes without being detected by a blood test. Compared with this, the percentage with anemia is about 5% or less for general adult males and 10% or less for female , which is about half that for athletes.

Hematological indices

It produces hypochromic microcytic anemia that shows low levels of red blood cell in the peripheral bloodstream, hemoglobin, and hematocrit. It may include decreased serum iron, increased total iron binding capacity (TIBC), decreased serum ferritin, and decreased serum iron.

Pattern of anemia

Iron deficiency, the first step in anemia, results in decreased iron stores but normal levels on peripheral blood tests. In mild anemia, tissue iron and serum iron levels decrease gradually. In the final stage of iron deficiency anemia, the red blood cells have extremely low levels of hemoglobin iron and serum iron.

Frequency by sport

Long-distance field athletes (especially females) and those who repeatedly run over a long distance, jump and contact sports such as volleyball, basketball, Kendo, and rhythmic gymnastics seem to be more likely to suffer from sports anemia.


In anemic conditions, iron supplements may be effective with dietary modification. If iron deficiency anemia is diagnosed, an oral iron supplement is the first choice. In doing so, take a combination of vitamin C and protein, which increase iron absorption. Exercise time and details should also be reviewed.

Typical Example 1

In the summer, a 15-year-old male basketball player exercised for 3 hours a day for 4 days a week in a gymnasium and developed general fatigue that required him to lie down during exercise a month later. The patient was initially considered to be truant, but a blood test for suspected hepatitis due to continued symptoms led to the diagnosis of iron deficiency anemia. The fatigue also disappeared with the cessation of exercise for about 1 month and administration of an iron preparation, and the test value was also normalized, so he returned to the sport. However, similar symptoms appeared in the summer, and the iron supplement was used in the summer.

Typical Example 2

A 17-year-old female terrestrial long-distance runner ran about 20 km a day for about a year and a half, but her performance stopped improving as her menstrual periods stopped and concentration in practice also decreased. Blood tests in the hospital showed extreme iron deficiency anemia, with hemoglobin 9.5 g/dL serum iron 40 g/dL, total iron binding capacity 420 g/dL, and iron saturation 10%.

Yasuhiro Nakajima

Yasuhiro Nakajima

Head coach of Shonan Bellmares Sports Club Triathlon Team, Head coach of Triathlon Team of Nippon Sport Science University, and Chairman of the Japan Triathlon Union Multi-sports Committee

Trainer’s Edition


Trainers suspect sports anemia if the athletes feel that they don't run as they used to, that they have no endurance, or that they are not concentrating. In sports that require cardiorespiratory endurance, performances are greatly affected by sports anemia. Exercises that require cardiorespiratory endurance, as aerobic exercise, require oxygen. Oxygen is taken up by the body and used for energy metabolism to maintain strong, long-lasting movements of the muscles. Hemoglobin in the blood transports oxygen to muscles throughout the body. It is well known that marathon, swimming, and triathlon players are trained at high-altitude, low-oxygen environments (high-altitude training) to raise the hemoglobin level.
However, sports that result in much perspiration cause iron to be released from the body along with the sweat. The landing impact of running also destroys hemoglobin in the capillaries of the soles. Sweating and such impacts can lead to the loss of needed iron.
Therefore, athletes should consume a lot of iron, which is the material for hemoglobin. Particularly for women, the menstrual period results in loss of iron, so caution is needed. Blood tests may need to show high levels of hemoglobin or of ferritin before it is converted to hemoglobin. The athletes should check regularly, and, if necessary, seek medical treatment such as administration of iron, as always suspecting anemia.

It is recommended to eat a lot of iron-rich liver, clam, freshwater clam, beef, tuna, Hijiki seaweed and Japanese mustard spinach on a daily basis. Large amounts of vitamin C and citric acid help the body absorb iron. Eating a diet high in vitamin B6 and animal vitamins, including vitamin B12 and folic acid, which help the body synthesize red blood cells, is important. It is important for athletes to eat a diet that is nutritionally balanced and does not focus on anemia alone. If necessary, take iron or multivitamin supplements.
It takes time for iron to change into hemoglobin, even when it is consumed in adequate amounts in the diet. Encourage people to maintain a balanced diet, such as iron and vitamins, for a long time.