Club head speed determines distance. The golf swing has three moving parts: your body, your hands and your arms, all of which generate power during the swing.

The upper body needs to make a complete shoulder turn on the backswing, (this is where energy is stored). On the downswing the arms drop and swing around the body, then the hands release through the impact zone to create speed by straitening the arms at impact. As the arms swing down from the top of the backswing and through the hitting area, the speed of the swing will continue to increase if the arms straighten during the impact area.

Years ago, while working at Cleveland Golf, I had the opportunity to watch many PGA Tour players practicing on the range. The longest hitters were the ones whose arms were soft and relaxed during the swing. At address, the arms should be relaxed and hanging down from your shoulders, tension free. At impact, the arms should be fully extended, allowing the hands to release upon impact.