2. SCT and Sporting Activities
All preventive measures described here in relation to the possible effects of intense physical exertion should be taken by all athletes in order to safeguard their health.
2.1. Is There an Increased Risk of Exercise-Related Morbidity and/or Mortality in the SCT Population?
Exercise-related morbidity and mortality in individuals affected by SCT are mainly linked to a very rare clinical issue referred to as exertional rhabdomyolysis and to exercise-related sudden death, which can occur under extreme conditions, such as severe dehydration and high-intensity physical activity.
Studies report that severe or fatal exertional rhabdomyolysis is attributable to a wide range of activities (football, training, cross-country racing, swimming, spinning, hockey, exercises in the army, etc.) in which the effort undergone by the individual can be classified as intense. The same studies also describe compartment syndromes, hematuria and isosthenuria 
During intense physical exertion, exertional rhabdomyolysis manifests as extreme muscle weakness and pain, even mild pain, which arises rapidly without prodromes. Rhabdomyolysis can be fulminant with muscle cell death, potassium release, hypercalcemia, and the death of the subject due to the fact of arrythmia 
Documented sports activities, the clinical picture and evolution, the causes of exertional sickling, and inducing and protective factors are summarized in Table 2.
Table 2. Exertional collapse associated with sickle cell trait.
Several studies conducted in a military environment and, above all in, football 
report that sudden death is the most dangerous complication in individuals, athletes, and soldiers with SCT 
. The risk of sudden death in recruits with SCT during intense exertion (assessed in 2 million military recruits in the USA) is estimated to be 30 times higher among African American individuals and 40 times higher than that in recruits in general 
. Death is mainly attributed to exertional rhabdomyolysis during the first month of training and during activities requiring high-intensity exercises 
. The increase in deaths correlates with age (higher at 28–29 years than at 17–18 years), probably due to the cumulative effect of renal papillary necrosis and the resulting isosthenuria, which is common in SCT (it is observed in 85% of individuals of the age of male recruits 
). In more recent studies, HbAS was associated with a higher adjusted risk of exertional rhabdomyolysis for military men (hazard ratio: 1.54; 95% CI 1.12 to 2.12; p
= 0.008). The risk was 57% higher in men >36 years old 
2.2. What Precautions Should Be Taken?
If preventive measures are taken, the risk of sudden death attributed to SCT seems to be zeroed 
Hydration and training with progressive exercises can “revert”/normalize some hematological abnormalities (increased plasma viscosity, oxidative stress, endothelial activation, and sickling) observed during exertion 
Coaches, athletic trainers, and medical staff should follow universal training precautions 
. Coaches must be aware of the potential dangers during training; therefore, they should avoid repetitive and intense activities without breaks and stop the exercises immediately and alert the doctor if an athlete shows signs of exertional rhabdomyolysis.
It is essential to prepare an emergency management plan in advance, as well as ensuring that the necessary equipment is available during all training sessions and competitions.
2.3. Can Individuals with SCT Practice Sports Activities and Undertake Them at a Competitive Level?
The benefits of (aerobic and anaerobic) physical activity in SCT carriers are similar to those experienced by individuals without SCT; therefore, SCT carriers should be encouraged to practice sports.
However, sports clubs and coaches must implement strategies to reduce any risks associated with the player’s SCT status; these include appropriate training and monitoring during training.
If the athlete is aware of his/her SCT status, appropriate precautions should be taken regarding individualized training methods and resting periods.
If the SCT status is not known, preventive measures should be adopted anyway to safeguard all athletes.
It is important that coaches and physical trainers are aware of the possible presence of SCT carriers among their athletes and that training sessions in general include appropriate rest intervals and hydration. In addition to this, coaches and trainers should be able to recognize the early signs of specific symptoms that may arise during physical exertion in athletes with SCT and to initiate early treatment.
No contraindications to sports activities are reported for athletes with SCT.
Only individual cases are reported in the literature; there are no studies with large numbers of splenic infarctions secondary to high-altitude flights in unpressurized aircraft or during mountaineering excursions. Usually, the altitude at which athletes can train or compete is between 2000 and 2500 m, and this is defined as a moderate altitude.
Intense physical activity at low altitudes is certainly a risk factor for rare complications, such as splenic infarction, sudden death, or rhabdomyolysis; rapid exposure to high altitudes and related hypoxia increase the frequency of splenic infarction episodes. In retrospective studies, over 90% of the cases of patients with splenic infarctions at high altitude were SCT and males.
In this context, hypoxia and physical stress are responsible for vaso-occlusion from sickling in the spleen red pulp. The splenic infarction of individuals affected by SCT is a benign condition that very rarely requires splenectomy and usually results in complete recovery with conservative therapies (rest, hydration, oxygen support, analgesics, and rapid patient transport to low altitudes).
Importantly, splenic infarction is not observed in SCT individuals who are native to or have been resident for many years in high-altitude locations; therefore, acclimation has a protective effect on sickling and its complications 
When individuals with SCT undertake sports activities of any kind at moderate altitudes or mountaineering at high altitudes, a specific acclimation program is recommended.
There are no reports of complications following scuba diving. Regarding the physiology of diving (increased oxygen concentrations and possible toxicity), a minimum increase in risk can be supposed during nonprofessional practice. However, in relation to the complexity of the exercises undertaken in the navy, diving is not recommended for individuals with SCT