“It's well known that physical activity has a positive effect in preventing both cardiovascular disease and depression," said Finn Rasmussen, professor of social medicine, in a statement.
The study at Stockholm's Karolinska Institute observed more than a million teenage boys in Sweden over a period of 24 years.
"But we have no data about teenagers' physical activity, only their muscle strength,” Rasmussen said.
The teenagers, all between 16 and 19-years old, had their strength measured by doing knee extensions, hand grips, and elbow flexes. Researchers also took their blood pressure and BMI into account.
“We can't answer to what extent the muscular teenagers were also physically active, and if this is an explanation for our results,” Rasmussen said.
Suicide and cardiovascular disease, major causes of death in young adulthood, were more prevalent with weaker teens.
The correlation to suicide and heart disease was as strong as known risk factors, such as obesity and high blood pressure.
The researchers claim teenage muscle strength should be considered a risk factor.
More than 20 percent of participants who died during the 24-year study killed themselves. Almost 15 percent lost their lives to cancer, while heart disease claimed another 7.8 percent.