I know my efforts in a slightly wider landing led to my 5km PR - there are indisputable torsional benefits gained by not crossing over.
Walk on a piece of string or along a seam in the concrete or walk on the lane dividing lines on your local high school or college track. What happens ? If you walk on a single line you will find yourself more unstable as compared to walking with a foot fall directly under your hips and knees the way it is supposed to occur. The limbs are a pendulum and economy and biomechanical efficiency as well as injury reduction will occur when the parts operate in the most effective manner.
We have all of our cross over runners, as you see her doing in the first half of this video before she corrects to anti-cross over (ie. natural), first walk on a line. In our case we use the metal drainage grate outside our office that you see in the video for just that purpose, they walk the grate. Then they run the grate. We ask them to feel ....... want to read the rest ? head over to our blog here for the entire article.
Here are the other related cross over links here on youtube:
Part 1: http://youtu.be/LG-xLi2m5Rc
Part 2: http://youtu.be/WptxNrj2gCo
Part 3: http://youtu.be/oJ6ewQ8YUAA
^^Thanks Gait Guys for articulating what I had to learn the hard way :)