I would say in General non veg people are stronger because in general they eat much more protein which you need to build strength and muscles. There are strong veg people as well since foods like nuts are also high in protien and you can take suplements. Also I bet you could argue that most veg people arent big in to weight lifting anyway. The mind set of vegitarian people would normally make them runners in my opiion. Of course there are always exceptions.