The type of chokes and cranks discussed here are designed for the street. Several of them have been banned from judo competition because they are too dangerous for sport. Since they may result in life-threatening injuries to your opponent, you must only use chokes when the situation warrants a high level of countervailing force.
Attempting a choke on the street without practice is a poor choice for combat, one that is very likely to fail. Supervised practice is essential.
You will most likely learn these techniques by practicing with a uniform gi initially. This heavy clothing not only facilitates many chokes, but also does not tear easily. Once you get good, practice with a t-shirt too. It is very important to be able to use these kinds of techniques in street clothes. Finally, practice against a shirtless opponent so that you will be prepared for every eventuality.
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