I have a problem when I lunge. Too often, my toes want to turn out - why does this happen?
First off, thanks for the question. I actually got a very similar question from one of my online clients, so I figured I'd address it here in the blog.
We know the gluteals (and in particular posterior glute medius) is often weak; this is really important when we are discussing frontal/transverse plane movements. Essentially, if your posterior glute medius isn't up to the task, you'll see an increase in adduction/internal rotation of the femur in single-leg exercises. In non-geek speak, your knee caves in.
To help improve your balance/stability, your body looks further down the kinetic chain. One of the primary lines of defense is to turn your toes/foot out, giving you a wider base of support. So while you'd think the issue was the foot, it's typically more of a hip problem.
If this is the issue you're suffering from, I'd incorporate either some x-band walks or band resisted clams into your program. These can be performed pre-workout, or even better still, immediately prior to the affected exercise. This will engage/facilitate the appropriate musculature in a lower level setting, and help it re-groove it's appropriate role in a motor integrated setting as well.
(Video clips can be found on my website if you are unfamiliar with the above exercises.)
Good luck and good training!