"A study of 6,000 San Francisco longshoreman showed that light workers had
2.5 times as many fatal heart attacks and 3 times the incidence of sudden
cardiac death as moderate or heavy workers."

"Weight lifting and isometric exercise do not qualify."

Cavemates, I have a problem with the above.  Lifting is moderate to heavy
work and lifting is also aerobic.

http://www.benbest.com/health/cardio2.html