Verga,
I am going to respectfully disagree with you. Being the Pack Alpha is not about physical dominance, it is about attitude. There is absolutely NO reason to physically force a dog into a down position by applying pressure to the head and/or neck.
One can very gently coax a dog into a down position with a tastey morsel and the dog is going to follow the food. Follow up the dog assuming the "down" position with positive verbal feedback and and another treat. Repeat repeat repeat.
Last week a co-worker brought her little terrier mix into the office. I happened to have a few dog treats in my coat pocket. I sat down on the floor and within 5 minutes I had her dog going into a down position on her own just by showing her the treat. I simply had let her smell the treat, then I held it in my hand down in front and ahead of her on the ground. She quickly realized that she got the treat when she lay down. She nailed it when others showed her a treat, also. It took her a few seconds to realize that these other humans wanted her to assume the "down" also, but she was very food oriented.
Anytime one has to HOLD a dog into position - that is not being Alpha. That is just pure physical dominance. Physical dominance = fear dominance.
A benevolent Alpha does not have to get physical. Mere posturing should be enough, sometimes supplemented by a quiet growl if warranted. If you ever watch a pack of dogs, the Alpha will rarely get physical. The Alpha doesn't have to. I have watched my canine Alpha male merely sit in front of the doggie door while the other 3 dogs barked furiously on the outside. They would not enter and go past him. He has also held an alpha wannabe in another room simply by laying across the doorway. The youngster barked and wiggled all over the place, but the canine Alpha male just ignored him. Of course, the Alpha canine bitch would just hop over the male canine Alpha. An canine Alpha bitch pretty much can do whatever she wants - the males don't usually mess with the Bitch. But then you human males understand that concept, don't you?
I have seen my canine Alpha male flip a pack dog over on its back (alpha roll) and straddle the dog when the dog started to get physical with him. No fight, no bite, just some growling, teeth baring, and a good talking to. Then he would walk away and the other dog would be as submissive as it could possibly be. No physical dominance - well, except for the Alpha Roll. Most humans cannot effectively implement an Alpha Roll and these are best left for canine behavioral experts and canine Alpha's to implement. Even with an Alpha Roll, the Alpha is NOT physically applying pressure to the head, neck, or muzzle. The Alpha simply gets the pack dog in a submissive position with a quick flip followed by a straddle.
Canines communicate by body language for the most part. There is polite communication and there is in-your-muzzle communication. Any good Alpha controls the pack by body language. That does not mean that there will not be any physical interaction or fights - there may be posturing and fighting for pack status - usually amongst the pack itself and less from the Alpha.
Any owner can use physical dominance and fear to control their dog. And then what you have is a dog who is afraid of you and not respectful of Alpha status. Actually, if you need to exhibit physical dominance, you aren't really the Alpha by attitude - you are just a more aggressive member of the pack.
Just my thoughts on physical dominance. YMMV.