But a good part of it is the breeding. Conformation (show) Labs and field (hunt test/field trial) Labs have diverged a good deal in body type and in activity level. Field Labs are slender and sleek not only because they are "on the go" all the time, but because they are bred for that "on the go" temperament AND a lean body type.
My dog is an odd bird, because she is one half conformation and one half field. Her dad is a simply gorgeous conformation Champion, who probably couldn't find a bird in a phone booth if you gave him printed instructions, and whose idea of exercise is a trot across a nicely mowed green lawn to pick up a tennis ball. Her mom on the other hand is the offspring of the only Chocolate Lab ever to win the National Field Champion title, bred to a Chocolate from the best field kennel in the country. She was the puppy most like her mother -- but she still is sturdier in build and wound a little less tight than Tori. Here they are exiting the very same tunnel, from the very same angle:
But people think Shelley is skinny . . . until they meet Tori.
Once it cools off a little down here, agility classes will be starting up at my dog trainer's (summer in Gainesville is exceptionally brutal). I don't know how Ursa will take to it, she really seems more inclined to therapy work, but I'd like to get her a regular work out and she needs something to strengthen the leg she broke. I think she'll jump at the chance to run around a bit, but those tunnels freak her out.
The one funny thing about rotties is they can be ridiculously clumsy and blocky, but yet can be so graceful when they really hit their stride. Last year, I was at the local pet fair sponsored by our science museum, and I saw a 115 lb. male rott complete an obstacle course in 11 seconds, beating a Jack Russell that was a quarter his size. It was amazing.