My TKD teacher busted our asses - it wasn't uncommon to do 100's of knuckle pushups a night as punishment for bad form, etc. Fist isn't clenched tight enough - the entire class did knuckle pushups. It was started as sort of a college intramural sport - had 80 or so people the first few weeks. He whittled it down to around 20 of us after a few weeks of intense workouts. 2 years into it, one of the activities we did was to kick our opponent across the gym. We paired up with someone of equal size, they got a 6" or 8" thick pad to block with, and we had to physically move them across the gym, from one end to the other, using the force of our kicks. The person with the pad was not allowed to yield an inch - every little bit had to be worked for. And, neither you nor your partner wanted to get caught just going through the motions and moving from one end to the other - both were pretty much knocked on their ass with a demonstration on how to do it. Essentially, you could put a 6" pad on 150 pounds of concrete, and be asked to move that concrete across a gym using nonstop kicking. Physically, he was incredibly demanding of us - I'll be turning 50 years old this year - I can still do a split, thanks to the amount of stretching we went through. We didn't just get lots of belts as rewards - every belt was earned.
Our teacher didn't focus only on TKD - he even admitted to its weaknesses in many situations (including close in), so when he was in the mood, he worked with us a lot on close up techniques. And, many of the techniques were situational, such as the most likely place to get into a fight - against someone drunk at a bar. His rule: never hit a drunk person; there was no need to assert that you won that way. In my 20s, if I wanted to, and you were wearing a ball cap, I could kick the hat off your head, leaving the bottom of my foot 1" in front of your nose. (I doubt my aim/control is that good now.) In sparring, thank God for a cup - both of my feet were lifted off the ground. I rolled around the floor while my sparring partner was doing pushups for lack of control. In the case of an untrained attacker coming at me, I'm confident that my odds are a hell of a lot better than they would have been without the training - if it turns into grappling on the ground, I'm going to lose. If it's someone who has spent a few years learning some other martial art, my odds might not be so good. But, I had a hell of a lot of fun learning, and it's a lot better than nothing.