For my internal martial artist friends... Pleasure of taking a couple lessons with Mark Cohen in Hawaii opened my world to true internal power and the possibility of it being used into old age. Didn't' understand or even grok what was being implied until recently. Internal power not excessive muscle power or forcing your way through. Being smart finding the correct angles and utilizing the specific taiji energies. Solving in many ways "how does a smaller older person defeat a larger younger opponent ? "
Doesn't matter what art.... Mastery occurs when someone discovers internal power and then the details and physics of how to use it. Methods clearly explain how to develop internal power and wave mechanics.... step by step in old yang style taijiquan.