Very interesting debate going on here. I am unaware of the kind of physical training US police academies give. I'd like to elaborate on my European academy training though.
In my encounters on the street, I've used arm locks and knee techniques a number of times. Pain stimuli (punches and kicks, in other words) are allowed though I've never had to use those. I used most of these techniques when the suspect was already on the ground and refused to give his hands in order to be cuffed.
The most difficult part (one that wasn't taught at my academy for that matter) for me, is engaging the first physical contact with an uncompliant suspect.
Not that long ago, I encountered a mentally unstable person who fled his mental institution. He had his arms tightly next to his body and froze up completely. Mind you, the guy was mentally ill and uncompliant though in no way a criminal. Although he refused to be taken back, he was very friendly and kept complimenting us for being his only friends.
Usually, I get quite an adrenaline rush when a suspect resists arrest. This makes me focus and makes me want to use physical force since it's me vs the "bad" guy.
With the mental guy, it was just me vs the "sick" guy. With a decent amount of luck, me and my partner managed to still make him comply without violence.
Afterwards, it made me wonder though what I would have done if he hadn't complied.
I'm not saying my academy training was useless. On the contrary, it gives me a couple of techniques to choose from when in a wrestle. It did not teach me, however, how to properly engage the first physical contact when a suspect is directly in front of me and refuses cooperation.
When I'm behind or next to the suspect, no problem. I'll use a choke hold or bring him to the ground with a arm/wrist lock. When he's directly in front of me with his arms tightly fixed, that's a whole different story. My department has a two-man police patrol policy so most of the time, bringing down a suspect is no problem. Once on the ground, he is all but lost. It still makes me wonder though how I would engage contact when alone.
Any experiences from you US one-man police patrol officers are much appreciated!