How muscular you are as a teenager may predict how long you live, at least if you are a man.
Swedish experts who tracked more than a million teenage boys for 24 years found those with low muscle strength - weaker leg and arm muscles and a limp grip - were at increased risk of early death.
The team behind the BMJ study believe muscle strength reflects general fitness, which would explain the link.
Experts stress the findings do not mean muscle building makes you live longer.
The effect of poor muscular fitness in those tracked was similar to well established risk factors for early death, such as obesity and high blood pressure.
When the researchers took into account these better known risk factors, they found the link between early death and muscle power remained.
Over the course of the study, 26,145 (2.3%) of the men died. The leading single cause of death was accidental injury, followed by suicide, cancer, heart disease and stroke.