Perform dips, push-ups, L sits, V sits, hand stands, and other bodyweight gymnastic movements. Increase upper body strength, balance, and body control with inexpensive homemade parallettes (PDF.)
Parallette training will unleash the gymnast within and develop that super-human gorilla strength. Talk about throwing a monkey wrench into your workout and confusing the heck out of your muscles. A steady dose of this will give those stagnate muscles no other choice but to grow stronger.