Are you talking about the brachioradialis? I ask because you said, "I pulled the brachialis muscle in the front of my left arm....". The brachialis muscle is underneath the actual bicep muscle. The brachioradialis is part of your forearm.

If you are talking about the brachioradialis, it could be caused by a muscle imbalance. I believe that the majority of people have stronger wrist flexors than wrist extensors. We are always gripping kettlebells, barbells or dumbbells and in doing this, our flexors get stronger. But our extensors don't. A muscle imbalance between the flexors and extensors can cause injuries like tennis or golfer's elbow.

Try working on your wrist extensors by putting a rubber band (or a few of them depending on the type of rubber band) at the tip of all your fingers and opening up your hand. Or you can just put a rubber band around an individual finger and the thumb and move them away from each other.

I am currently fighting off some tendonitis around the same area and the rubber band exercise is working out very well. I've always had weak forearms and it's finally caught up to me. I've iced my arms, took more fish oil, stayed away from the weights and all that but it seems like the rubber band "training" is working the most. I've had to lay off training for over two months but now I'm getting close to going back to training.

Good luck and keep us informed on how everything works out