Is training my dog to pull a sled a bad idea?

Ok I know this is going to sound crazy.But I have an English Springer Spaniel.I live out in the country and own roughly 6-7 acres.Well we normally go out running everyday and go down to the pond and swim.But the colder months are coming up.So I need something to do so she won't get fat.So I was wondering if I could teach her to pull a sled.I know they are not bred for that but I love sled dogs.So here is my question.Would it put any strain on her if it was just a small sled that weighs about 2 pounds?