Running form is very important when it comes to speed. If your legs, or arms do not move in a motion that helps bring momentum forward, then your body will not run at an optimal level. You should spend time working on running mechanics. This specific drill is built to focus on arm action.
Place your arms in a 90° angle and begin slowly. Athlete should bring their hands near their chin before driving it back. Notice in the video the complete range of motion forwards and backwards. Stay in line. Do not swing your arms from side to side or straighten at the elbow too much. The faster your arms move, the faster your body will run. Notice athletes at different levels can still have proper arm action when running. Utilize this drill as a warm-up before doing sprint training. The extra work will pay off.