Exertional sickling is a potentially life-threatening condition that can occur when individuals with sickle cell trait engage in intense physical activity. It involves a change in the shape of red blood cells.
The Basis in Sickle Cell Trait
Sickle cell trait (SCT) is a genetic condition where a person inherits one normal gene for hemoglobin and one abnormal gene for sickle hemoglobin. Hemoglobin is a protein within red blood cells responsible for transporting oxygen throughout the body. Unlike sickle cell disease, where two abnormal genes are inherited, SCT typically does not cause health problems under normal conditions. Under specific extreme physiological stresses, their red blood cells, which are normally round and flexible, can change into a crescent or “sickle” shape. This genetic variation is relatively common, affecting millions worldwide, including approximately 1 in 12 African Americans.
How Physical Activity Causes Sickling
Intense physical exertion creates an environment within the body that can trigger red blood cells to sickle in individuals with sickle cell trait. Factors such as low oxygen levels, the buildup of lactic acid, increased muscle temperature, and dehydration contribute to this process. During strenuous activity, muscles demand more oxygen, and if supply is insufficient, the environment becomes oxygen-deprived.
This lack of oxygen, combined with metabolic changes like lactic acid accumulation, causes the sickle hemoglobin within red blood cells to clump together. These rigid, misshapen cells can get trapped and block small blood vessels, impeding blood flow and oxygen delivery to muscles and other tissues. This blockage can lead to muscle breakdown, a condition known as rhabdomyolysis.
Identifying the Symptoms
Symptoms of exertional sickling often appear suddenly during intense physical activity, sometimes within the first few minutes. Individuals may experience intense pain, overwhelming fatigue, and a feeling of being unable to continue exercising. Muscle weakness is a common presentation, often causing the athlete to slump to the ground. Unlike typical muscle cramps, the affected muscles in exertional sickling may not show visible twitching or hardening and can feel normal to the touch. Other signs include difficulty catching one’s breath. It is noteworthy that the core body temperature of an individual experiencing exertional sickling is usually not significantly elevated, which helps differentiate it from heat stroke.
Management and Prevention Strategies
Immediate action is essential if exertional sickling is suspected. The individual should immediately stop all physical activity. Emergency medical services (EMS) should be activated without delay, and vital signs, such as heart rate and breathing, must be checked. Administering high-flow oxygen, if available, can help to reverse the sickling process by re-oxygenating red blood cells. Cooling the individual may also be necessary, depending on environmental conditions. Transport to a hospital is important, with medical personnel informed about the suspected exertional sickling to prepare for potential complications like rhabdomyolysis.
Long-term prevention strategies focus on modifying exercise practices for individuals with sickle cell trait. Maintaining proper hydration before, during, and after activity is important to reduce risk. Gradual acclimatization to heat, humidity, and altitude is advised, as these conditions can increase vulnerability.
Adequate rest and recovery periods between intense exercise bouts, particularly for activities like sprints, are also beneficial. Individuals with sickle cell trait should be encouraged to set their own pace during exercise and avoid “all-out” exertion, especially for prolonged periods. Avoiding exercise during illness or fever can also help prevent an event. Educational efforts for athletes, parents, and coaches are important to ensure awareness of exertional sickling’s signs and symptoms and appropriate preventive measures.