It's actually a lot more complicated and specific than that.
Let's take an armbar for example, since it's probably the quintessential BJJ technique:
All lever systems have a fulcrum/pivot point and a "lever"/rigid structure through which force is applied to create kinetic energy/move a load.
The law of the lever states that the longer the lever arm the less force must be applied to create force at the other end of the lever. In fact, if we double the length of the lever, we half the amount of effort required to produce the same amount of output and likewise if we cut the lever in half we double the effort required to produce the same amount of output.
In an armbar we can use this knowledge to our advantage in several ways:
1) by being as far out on our opponent's forearm as possible (thus making our lever as long as possible)
2) by placing our lever/opponent's forearm as close as possible to our fulcrum (in this case our elbow joint)), thus creating the shortest possible lever for our opponent to utilize to attempt to bend their arm
3) by placing out hips/fulcrum as close as possible to our opponent's elbow/their fulcrum, thus again creating the longest possible lever to utilize to create our output and utilizing the power of our hip to extend their elbow
In powerlifting we can use their knowledge as such. Let's take a look at the bench press as an example:
1) by maintaining a vertical/in line with gravity forearm orientation at the bottom of the press we maximize leverage at the elbow joint, thus allowing us to maximally transfer the forces we produce through our lower arm bones/levers into the bar
2) by utilizing either a false grip or by placing the bar diagonally across our palms (so that it rests on the Ulna bone/pinky side of the Palm heel) we create as short of a lever at our wrist as possible, thus minimizing the forces needed to maintain a solid wrist alignment
3) by utilizing maximal back arch we seek to minimize the distance that the bar must travel and if possible to allow bar contact at a point that is shy of having our upper arm bones being perpendicular to the line of gravity/parallel to the floor (which is the point at which we are working against the longest possible lever and thus must produce the most force to move the bar)
The better we can do these things the more weight we will be able to lift with the same strength levels.
If we were going to apply it to bodybuilding, let's say a biceps curl, we could utilize it like this:
The biceps produce three joint actions-supination of the forearm, elbow Flexion, and shoulder Flexion
So, in order to best contract our biceps we must fully supinate the forearm, fully flex the elbow, and fully flex the shoulder AND we must set up a condition where we are working against the longest possible lever at this point in the movement.
In order to do this we are going to have to utilize an adjustable cable attachment and either a straight bar or two independent handles (to allow for maximal supination), a bench to place our elbows on as we bring our elbows "overhead"/chest to the floor as much as possible/flex our shoulders, and set the cable attachment to a height so that when our elbow is bent maximally the angle between our forearms and the cables is 90 degrees. If we set this up correctly and actively try to maximally supinate, actively flex the shoulders, and flex the elbows as much as possible we can achieve the most possible contraction in the biceps while building strength and maximally challenging/stimulating the muscles in this most contracted position.