During weighted (and not weighted pull-ups and chin-ups) my forearm tires first and the most and I do not actually feel back and biceps at all. Does that mean my forearm is relatively weaker and I need to work on it separately to improve pull-ups/chin-ups (weight) overall?
my routine is described in other question
Yes, you can perform grip work as suggested by Alec. In the meantime consider using straps or at least chalk for hands to increase friction and combination of the two would improve your 'feel' in a given muscle. Consider as well is the weight that you are pulling too heavy for the goal you want to achieve? Regards
Yes. This is a normal problem to have, but one that is easily (but slowly) fixed by simply taking 5 minutes or so every workout to do some grip work.
For instance, if you're doing deadlifts, do some bar holds after your last set/rep. Just stand there, and hold the bar. Adjust the weight if necessary.
After you're done with pullups/chins, do some dead hangs.
My personal favorite is the farmer's carry. If you do these, you can't help but develop a strong grip.
Yes, strong forearms are necessary for achieving high reps and weighted reps. If you want to increase your grip strength, dedicate a few days to simply performing dead hangs with the weight you plan to do pull-ups with. This may "feel" like you're not doing anything but in reality, you're conditioning your arms to hold on and creating a good posture for future pulls.
Try performing the dead hangs for a minimum of 35 seconds each time and work your way to 60 seconds. You'll notice a difference when in your grip once you can hold 60+ seconds.
This is actually what is expected from the standpoint of biomechanics.
All pullups technically have a "greater mechanical advantage" in favor of elbow flexion (brachialis + brachioradialis) over shoulder extension (lats + rear-delts) from the bottom of a "dead hang" position all the way up until your upper arm is "horizontal" or parallel to the ground. And only from there, until you reach the top of the movement with your chin way above the bar, does the mechanical advantage for shoulder extension exceed that of elbow flexion.
And so, since the body generally chooses the "easiest way possible" to do an exercise, it's not surprising you end up feeling the exercise primarily in the arms/forearms rather than your back/shoulders -- especially if the latter are already too strong for the former to keep up with them during the exercise!
