Recently I wrote about the riders seat and hands, here is my interpretation of how to use the hands and arms effectively.
Ideally, the upper arms and elbows should remain comfortably resting by your sides. The elbow becoming the heaviest part of your arms. Carrying your upper arms and elbows in front of the body upsets the flow of gravity through the joints. Imagine walking with your upper arms and elbows in front of you, as if you were pushing a pram. Would you feel balanced? How about holding this position while running? The weight of your arms will drive you forwards. It is almost impossible to carry your arms in this manner on the horse without exerting a certain amount of pressure on the horse's mouth. Try while you're sitting down now, hold your arms in front of you as though you were pushing a pram. How long can you maintain this position? Not too long without some kind of support? In the saddle, the reins act as a support for the arms, which naturally travels down the reins, to the bit and therefore the horse’s mouth.
It is more natural to carry your upper arms by your sides, after all, the riding is all about natural balance. Do not grip with your elbows because this will not allow freedom of the horse's jaw. Be soft in your fingers, and give with your elbows. Riding with a clenched fist will cause tension in the body as it travels up your arm and to the upper body, holding the reins softly, but firmly, like the proverbial baby bird, you don’t want to squash it, merely prevent it flying away.
Connection begins in the seat and is collected by the hand.
Always strive for that imaginary straight line from Ear - Shoulder - Elbow - Hip - Heel.