Overhand pullups - inner forearms ache but why?

Question

I can do underhand pullups quite comfortably (working the biceps), but I find the overhand ones more difficult, almost certainly because my back muscles aren't as strong as those at the front.

On Sunday I did a mix of under and overhand pullups (70 & 25 respectively), and tricep dips.

On Monday I did six sets of ten overhand pullups in the course of an hour (I was doing karate practice). I felt very strong and did them better than those the day before. But over the course of the day and even now, my inner forearms hurt when I open my hand fully, or flex my hand in (palm faces the body). The ache is below the wrist, in the middle. Images on Google show this could be the Flexor Carpi muscles, I guess strained.

My question is why would these muscles ache and not my upper back (which I assume is what gets worked in overhand pullups)?

UPDATE: I no longer have this issue. I switched to wide-arm pull-ups as advocated by Arnold Schwarzenegger and Nick Aldis, doing 50 reps over 3-5 sets on a regular basis and it is going well. I believe my forearm muscles were not used to the exercise and I was overtraining. Rest and working on flexibility have both really helped.

Answer 1

This is a common issue that arises due to limited mobility in your forearm.

While you might be inclined to start doing underhand or neutral grip instead, I would strongly advise that you try the false grip instead.

This is indeed a challenging thing depending on your forearm strength, but you can progress into it by simply gradually placing your grip higher and higher on the bar.

In addition to relieving a lot of tension on the brachioradialis (which is most likely the issue you're having), it also contributes greatly to your forearm strength.

In any case, I would always recommend varying your grip from time to time, but you should never avoid the overhand grip unless you really, really have to. Specifically because, as you mention in your question, it tends to utilize the back muscles in a more significant way. That's generally what we look for in our pullups.

Answer 2

I cannot give an expert answer, but from my amateur experience, this might actually be a flexibility issue. I know that I, not much of an overhand pullup guy, find that rotating my wrists to the overhand position is already engaging the muscles a bit to keep them there, even without the pullups, because it's not a usual position for me in my day-to-day life. Now, add the exercise of actually doing the pullups and that means you have some degree of effort going on in that muscle at all times (plus, ligaments pulling, etc). Compare that to your back, which not only has larger muscles, but probably gets to relax a bit as your going down.

According to this answer, there's a good chance that your brachioradialis muscle is what's hurting. Pay attention to your body. Take a break when it starts hurting and be patient as you make gains.