I respect the opinions here. One question is whether 'one shot' delivered with the mass of a person can cause a crippling injury. People fall all the time, and they don't get hurt. Another person falls in the 'correct way' (in our example of causing injury) and he's injured and can't use that limb for the time being; even if he's high on drugs or has a high pain tolerance, he still can't use that limb. We see in sports where someone's mass accidentally and immediately causes an injury, and the guy has to be carried off the field after 'one shot.' So obviously, one shot can cause a severe injury. The question is whether this is likely with a moving target. I'm not going to address a 'street fight with rules' where the guys are 'ready to fight.' I'll just address the scenario where street predators want to injure or kill just for kicks. I do know of cases such as this: a guy is walking at night from work, guys run at him from behind. He may feel a strike to his back or whatever, and he immediately drives through one guy's neck; that guy drops. He attacks the second guy (there's a third) and drives his mass through that guy and pounds him. The third guy runs. There have been several real life encounters like this. Another rather 'funny' encounter was when a 6'6" guy went at a guy 5'6", 180 pounds. The little guy just bum rushed him and drove his mass (the old adage 'I'm standing where you were) and was pummeling the guy on the ground when a big cop (a weightlifter) lifted the little guy by one leg and asked him politely to calm down. In neither of these cases did the 'targets' have huge formal training; someone just taught them the basics or they figured it out. While the latter example is a 'streetfight' what I'm more interested in is the life or death encounter that is decided in a few seconds. So I would definitely side with Bruce Lee's adage to get it over with in a few seconds, and assume there are multiple targets with weapons. If there is no chance to escape, then you have to decide now if you can actually cause trauma. If the trauma will be done to you, it will be all over in a few seconds, anyway. One last word on 'mass through the target': I've seen a 'streetfight' (these are things one can elect to walk away) where two guys jumped on a truck, one guy picked up a pipe wrench and bashed the other guy, didn't even faze him, and they continued fighting. I just walked away. Was the guy with the wrench actually trying to seriously injure the guy? Maybe he had second thoughts as he swung it. Jack Dempsey wrote an interesting book based on his experiences with teaching 'war fighting' to Coast Guard. In the intro, he writes: a 20 pound baby falling from three stories can kill an adult man walking in the street.