The normal respiratory rate for dogs is 16 to 20 breaths per minute. The normal heartrate is 70 to 160 bpm. Large dogs tend to have slower heartrates so your dog should be in the 70 to 120 bpm range. This varies according to the cardiovascular fitness of the dog, too. The more active the dog is the slower its resting heartrate will be.
Many dogs are overweight and many dog owners feel their dog is too thin if they can see any ribs.
It is better from a health perspective to be a little too thin than to be a little too heavy, though. Breed size determines when bone growth stops. Little breeds may be fully grown by 6 or 7 months of age while giant breed dogs may continue to grow for 18 to 24 months. Most pitbulls are probably their full adult size, except for muscling and fat deposition, by the time they are a year of age. This seldom works in Puppy Mill dogs as their diet is so bad that their teeth age quickly.