Why do I suffer from numbness and pain in my forearms after working out?

Hello. Thank you for taking an interest in your health. It's always good to get to the lowest common denominator.

I would have to say that probably what you're experiencing is very similar to what people in my TRX classes experience when they first begin. Generally speaking, we have a tendency to "over do" things. As a result of this, we sometimes use muscles that are non-essential to what we are doing. It is very common to grip to tightly when we exercise.  One of the greatest things about fitness (which is often overlooked) is that you learn to feel your body in a different way. 

From now on, when you perform exercises that require gripping or pulling, try to only use the muscles specific to the particular exercise. If it is, however, a sharp pain; then it might be a good idea to see a physician. I hope this helps. Thanks for your question.