Not necessarily. We've got a machinist where I sit who's my age (early 60's), and he's about as hale and hearty and robust as any kid the same size - he still schleps 100 pounds of steel around like it's a feather, where to me, it feels like it's bolted to the floor.
But he's been doing that stuff for the last 40 years, while I've been mostly sitting at a desk.
Cheers! Rich