This article from 2011 was lightly edited and updated for new resources in 2020. If you're interested in feet, check out Our Favorite Feet, Footwear, and Walking Resources.
Like tires on a car as you're moving forward, the human feet, on a body moving straight forward, give their best leverage when pointing forward. It is in this position that the levers and pulleys of the ankle can be maximized, the arch-shape can be created by muscles of the feet and hip, and the toes can be more free to move. So, in classes I'll often start by having folks adjust their stance until it looks like this:
(I got this photo from www.pigeonsaspets.co.uk and I highly recommend visiting the site to learn more than you ever wanted about pigeon feet. Turns out they are amazing!)
Then I explain that, although the toes are very close to your feet, toes are separate, individual structures from your feet. Toes have their own muscles and those muscles can pull the toes wherever the heck they want to.
And the cool thing is, if you are duck-footed (feet turned out):
(Wait, is this a picture of a pigeon-toed duck? I'm so confused! Who came up with these names?)
As I was saying,
When your feet turn out as your leg swings forward while walking, your toes are sort of thrown forward a tiny, almost invisible bit. If your feet have turned out when you walk for a long period of time, the toes are accelerated forward with each step, and over time the toes are positioned forward relative to a turned-out foot. When you position your feet straight forward, your "forward toes" now pull medially (towards the midline).
“Don’t worry” I say. It’s just muscle and you can stretch that out. This is why we have lots of toe exercises, so you can start strengthening your toe muscles. I also recommend toe-alignment tools (see Correct Toes, and foot alignment socks).
I am also often told, “But I was told in my yoga class that the correct position of the foot was to line up the second toe.”
So then I say, "Yes. If your foot had been a forward-positioned foot the entire time you’ve been up and walking around, the second toe would have been parallel to the outside of the foot, see?
But if you've had the habit of walking around in turnout, the toe has moved away from where the second toe is assumed to sit, so the second-toe guideline doesn’t apply in every case. So many folks are now walking in turnout, if often doesn't apply, so when it comes to corrective exercises or teaching movement to move certain parts in certain places, we need a better, less-malleable way of seeing where the feet are.
This is why we use much less malleable points on the feet when we align our bottom half, instead of using the second toe. Toes are not attached to the foot in a fixed way, where they could be a reliable way to determine foot position. Toes are like teenagers. They can do what they want.