I am always interested to watch the quality of a runners arms. I find it can give so much away about a persons running but arms are so rarely considered an important part of running.
Two of the most common things I see are thumbs sticking up as if thumbing a ride. This to me is an indication of tension right through the arms, shoulders and chest.
The other thing I see is abandoned arms that are just not really involved in the running and a bit too floppy. Try running with your arms by your sides and you will see how tricky this can be.
Arms need to be part of the whole movement of running. Not overly tense or held but freely moving as part of the whole coordinated movement of running.
So whats with the peaches?
Well next time you are running begin by just noticing whats happening in your arms. Are they tense and held tight to your torso? Are they not really part of your running, just floppy and not really involved.
Then just imagine you have 4 soft juicy peaches, one under each armpit and one in each hand. You are going to need to allow some space between your torso and upper arm so that you have room for the peaches, maybe this allows you some more freedom at that upper arm joint.
And you don't want to squash them in your hands. So you need just enough tone so that you don't drop them but not so much they will squash. Don't worry too much about the position if you prefer your hands to be be more open that's fine, it's more about the idea.
And that's it that's all the tone you need.