Despite the famous link between ALS and baseball great Lou Gehrig, a new study shows that there’s no medical link between the disease and physical activity.

Researchers found no association between increased physical activity and the risk of developing ALS (amyotrophic lateral sclerosis). Those results contradict several previous studies that have shown that slim, athletic individuals may be more likely to develop ALS.

ALS is also sometimes called “Lou Gehrig’s disease,” (search) after the famous baseball player whose career was cut short by the disease, which gradually erodes muscle strength. Although ALS is often very disabling, many people live for years with the disease. The average life expectancy is only two to five years.

ALS and Physical Activity

In the study, researchers compared the amount of physical activity reported by 219 people with ALS with 254 healthy people.

All of the participants were asked whether they engaged in sports as youngsters or as an adult or whether they performed extreme physical activity. They reported total physical activity levels as well as activity levels in three different phases of their lives: before age 25, the last 10 years before symptoms of the disease emerged, and one year before the start of the disease.

“The results showed that there were no significant association between risk of developing ALS and increased occupational or leisure time physical activity,” says researcher L.H. van den Berg, MD, PhD, of the Rudolf Magnus Institute of Neuroscience in Utrecht, the Netherlands, in a news release.

“However we did find evidence to suggest that in those at risk of developing ALS for reasons other than physical activity, a higher level of activity could accelerate the onset of the disease; although other exposures during physical activity might also explain the association with early onset ALS,” says van den Berg.

The study showed that in people who reported high levels of physical activity in their leisure time before age 25, the disease began seven years earlier. Among those who reported high levels of leisure-time physical activity during the 10 years before the start of the disease, the onset of the disease was three years earlier.

ALS is a disease that affects the nerves that control muscles, and researchers say increased physical activity may cause more free radical damage to these cells and cause them to die.

But they say other risk factors that a person is exposed to during leisure-time physical activities might also explain the association with ALS starting at younger ages in people with high levels of leisure-time physical activity.

By Jennifer Warner, reviewed by Brunilda Nazario, MD

SOURCES: Veldink, J. Neurology, Jan. 25, 2005; vol 64: 241-245. News release, American Academy of Neurology. WebMD Medical News: “Athletes and Lou Gehrig's Disease.”