I had this problem for about 3 years…Tried everything small hurdles, fast skips, max frequency on top speed. All I did was wasting my time over this.
The only thing that worked well was to simply close my hand when I ran to avoid going farther than 90 degree at the elbow(thus increasing tension in the arm). For some people, open hands leads to too much relaxation in the arm which cause greater arms amplitude.
The root of my problem was simply long arm cycling. I have tried this also with some friends who had the same problem and the thing worked well.
Good luck!