Arm Swing when running

Doing a couple off long runs the last couple of days, and today I covered a good fifteen k.m and concentrated on my arm movement by not moving my elbows past my body. Many distance runners make running appear very easy for them self,other runners look as if they have to work quite a bit harder to maintain pace.When I'm running I go through different stages of running the foot striking the ground a bit ahead of the body , this is the start of the running stride, the things that happen are that the knee flexes ,the ankle flexes and some joints pronate a bit,and all this helps the body to absorb some of the shock of uneven ground or to keep your balance.It is important to remember to keep your feet straight and pointed in the direction you,r going, if your feet is pointed outwards you could end up with more stress on the knees and you cover less distance.Also over striding will cause you to lose pace and energy. But the faster you run the longer your stride becomes, but this all depends on your leg lenght, hip movement,and oxygen intake,While all this is going on your arm movement should be relaxed the elbows should swing forward and backward around a ninety degree angle and your hands should not be clenched. Run hard-- Run Smart