There are many techniques in BJJ and Judo which involve stiff arming your opponent, in order to create distance between you both. You see this often used when the bottom player is trying to regain his guard, or when setting up certain takedowns.
This blog post is going to go through a few exercises which are fantastic at developing stiff arm strength, and will help tremendously if you feel you are constantly being out-powered on the mats
Decline Barbell Press
The Decline Barbell Press is one of the very most important exercises when it comes to developing stiff arm strength. The rational behind this being that in most cases, it is the variation of a bench press in which you should be able to lift the most weight, therefore developing your pressing strength at the quickest rate.
The next important strength builder is the Floor Press. This can be done with either Dumbbells or a Barbell, single or double arm. The floor press lends itself to BJJ very well, as we often find ourselves required to generate power with a limited range of motion. The floor in this case acts as a barrier, as it does when grappling, and forces you to produce strength under slightly unconventional circumstances.
Single Arm Press
The Single Arm Press, (conventionally performed with a dumbbell, but can also be performed with a kettlebell), is #3 on the list when it comes to developing stiff arm strength. The difference between this and the rest, is the added benefit of developing anti-rotational trunk (core) strength. We often find ourselves needing to push with just one arm at a time (more so with standup), instead of two. This requires a little more strength to be drawn from the hips and core, which is developed admirably by the Single Arm Press.