Strenuous exercise is linked to motor-neuron disease

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ILLNESSES ARE often named after those who discovered them. An exception is a motor-neuron disease called amyotrophic lateral sclerosis (ALS), which is widely known as Lou Gehrig’s disease after a famous baseball player of the 1920s, who died of it. As the name of its class suggests, ALS kills motor neurons—the cells through which the brain controls so-called voluntary muscles, including those for moving, eating and breathing. Some 10% of ALS cases are inherited. What causes the rest is unknown. A long-held hypothesis is that strenuous exercise has a role, because the prevalence of the condition among athletes and those serving in the armed forces is several times that in the general population (where the lifetime chance of diagnosis is one in 300).