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If you are looking to hit the golf ball further than you currently do, then you should work on relaxing more, especially with your grip pressure.
If you grip too tightly, your muscles in your hands, wrists and arms tighten as they become tense. When your muscles are tense, they contract and shorten and as a result of this, the distance between the club head and your shoulders shortens, effectively moving the club head up off the ground towards you. As a result of this you will now swing the club and strike the upper part of the golf ball, producing a low trajectory golf shot. Due to the low trajectory, the golf ball will now land much sooner than a correctly struck shot would and as a result it will not travel as far.
In order to strike the ball more from the centre of the club face and to create a higher trajectory that allows the ball to travel its maximum distance, you need to relax your grip pressure. If you squeeze the golf club handle as tightly as you can and we call this a 10, you need to relax the pressure in your hands to half of this, to a 5. Now from here relax to a 4 and this is the ideal pressure to hold the golf club at, so that you are holding rather than squeezing the golf club handle.
Work on maintaining this pressure throughout your golf swing. You will now swing the club and return the club head through impact at the correct height, allowing you to strike from the centre of the club face, which in itself produces more distance. Every quarter inch you strike away from the centre of the club face, your shot loses approximately 10% of distance. So striking from the centre produces maximum distance. However, you will also hit a higher trajectory shot and this will see the ball in the air for longer before it lands. The longer the ball is in the air, the further it is travelling so the longer the shot is being hit.
The more relaxed your muscles are in your hands and arms, the more you will be able to rotate and turn your upper body as these muscles will also be more relaxed. The more rotation you achieve in your upper body, the bigger you are making your swing arc, or the circle that the club head travels around you on.
If you are tense and as a result can only make half a shoulder turn on your back swing, you only have half the amount of time to swing the club and as such you will not generate as much club head speed as you would if you made a more complete shoulder turn. With less club head speed transferring from the club head into the golf ball, the ball will be hit a shorter distance. To improve your distance and hit further, relax more to make a bigger swing.
Sorry Try Again! - See Explanation Below
Gripping the club tighter to try to hit further results in the muscles in your hands, wrists and arms shortening as they become tense. As a result the club head rises from the ground and this produces a mis-hit golf shot which flies low and not as far.
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Swinging harder will not produce a further golf shot if you are swinging that hard that you are off balance and lose control of the club head. If the club head does not strike the ball correctly and impact the ball from the centre of the face, then you will not achieve maximum shot distance. Centre strikes achieve this.
Sorry Try Again! - See Explanation Below
Tensing up in your body results in you not being able to rotate your body as well as you could. Less body rotation results in a lower club head speed being achieved and if you are looking to hit your furthest golf shots you need to increase your club head speed, not decrease it.