[comdpa]

Indeed the muscles you pointed out would cock and uncock the wrists and pronate and supinate. Although muscles of the upper arm would also help in pronation and supination of the forearm- so if you were trying to strengthen those- then you would want to also strengthen the upper arm muscles. However, none of the muscles that you described would move the hands faster through space. So to me, Sean's quote is just another quote that doesn't make any sense or is very unclear.

Sorry Mike,

When he related Jack Nicklaus' compliment, he was uncocking and rolling his hands - very quickly.

To him , handspeed was the sequenced release of the swinger - uncock and roll.
That said, I agree with you on the role of the upper arm but I still do not completely understand its role in producing clubheadspeed thus have not began isolating them in training yet. I will be most keen to share once I reach a conclusion.

One thing that stuck in my mind about Sean was the size of his Extensor carpi radialis longus and his Pronator teres. They resembled sausages.