I agree with wolfsoul.
Even if you are standing right by the dog, even if you are holding the dog ... if it decides to jump, it's going to jump. This isn't much of a problem with a small dog. Ten or twenty pounds of dog is easy to stop. However, with a large dog, take the weight of the dog ... which is sometimes more than half a person's weight ... and add the velocity and force the dog is using to propel itself, and you have a 150 pound groomer trying to stop 75 pounds of solid dog, plus at least that many additional pounds of velocity/force. Sometimes it is NOT physically possible. Of course, you do all you can and others immediately help, but ANY groomer is flat out lying to you if they say this never happens. It happens with the normally calmest dog, and the best, most experienced groomers in the business. Animals are unpredictable, at best. They can't speak and tell you, "Hey, I really have to pee. I'm going to try to jump off the table and try to run to the door." or "Hey, I really like to snap at flies, and there's one over there!"
Choke nooses are not a good idea, IMO. We don't use them. But, I know of a lot of groomers that do. They are not that uncommon.
Belly straps are very common, and normally very safe. If you are trying to groom a dog that sits down constantly you have no other option. You can't use one hand to hold up the dog's rear end during the entire groom ... you can't groom a dog with only one hand free! I've personally never heard of or seen any damage ever come to a dog from a belly strap, and I've been doing this a long, long time.
Personally, I think some irresponsibility lies with both the groomer and the owner here. Obviously the owner knew before this groom that the dog was difficult to groom. She said, "She has never liked to be groomed and I take her to the vet to tranquilize her to clip her nails." IMO, if you have a dog that has to be tranquilized for something as simple as nail clipping, and it is a large, strong dog like a collie, you ought to assume that there are going to be problems with an entire groom. If that were my dog, I would have had it groomed at the vet's when it is already tranquilzed for nail trimming. She knew it was such a problem that it had to be tranquilized, she saw the groomer having problems to the extent that she had to help hold the dog. The dog had to be muzzled after biting both it's own owner and attempting to bite the groomer. And yet the owner wants to not only continue the groom, but goes outside for a while. I understand her reasoning to some degree - sometimes dogs DO calm down when their owners are gone - but it sounds like it should have been obvious by this point that the dog was very stressed and should have just been taken home.
And, likewise, the groomer should have, "I'm sorry, but this dog is too stressed, too strong, and too aggresive. You and I together can't control her, and she is biting us both. You need to speak to your vet about sedating your dog to be groomed." Then she should have sent the dog home. There are dogs that simply are NOT groomable. Many groomers try to groom them anyway because they don't want the owner to be angry with them for not grooming their dog, or to speak poorly of their grooming shop. I've had people call me and say, "I took my dog to ABC grooming shop and they said they couldn't groom him. Can you imagine? They are dog groomers - and they can't groom a dog! I'm so angry with them. I want to make an appointment with you instead." Some groomers try to avoid unpleasant situations by attempting to groom dog they should just send home. It frankly takes some years of experience in dealing with both dogs and customers to learn to be assertive enough to say no. Sometimes, the customer is NOT always right.
The groomer could have certainly been more gracious and understanding with the owners. That is not good customer service, to say the least. Of course, we are hearing one side of the story. Perhaps it absolutely accurate, but perhaps, the groomer would have a different take on the conversation entirely. We'll never know.
There are, sadly, horrible groomers in the business. And there are, sadly, owners who aren't aware of or don't want to admit that their dog is not a little angel by any means. And of course, there are wonderful, kind, caring groomers and onwers as well. We hear about the 1% of dogs that have a bad time at the groomers, and we hear from the 1% of groomers who had to groom Cujo. The other 99% of the time, the skilled, careful groomers grooming basically well-behaved dogs, no one hears about. Grooming is a TOUGH job. If it were simple, easy and fun ... everyone would do it at home in their bathroom in an hour.
"We give dogs the time we can spare, the space we can spare and the love we can spare. And in return, dogs give us their all. It's the best deal man has ever made" - M. Facklam
"We are raised to honor all the wrong explorers and discoverers - thieves planting flags, murderers carrying crosses. Let us at last praise the colonizers of dreams."- P.S. Beagle
"All that is gold does not glitter, Not all those who wander are lost; The old that is strong does not wither, Deep roots are not reached by the frost. From the ashes a fire shall be woken, A light from the shadows shall spring; Renewed shall be blade that was broken, The crownless again shall be king." - J.R.R. Tolkien