There’s a widely believed theory—known as the principle of least effort—which might explain why you struggle to make a good golf swing.

The theory suggests that people instinctively choose the path of least effort when performing any activity. You don’t zigzag from your car to the front door, right? You walk straight in.

Same with golf.

When you swing a 450-gram golf club, your instinct is to use only your arms because that all the effort you need.

Unfortunately, to swing a club properly, you need to move more than your arms. The bigger muscles of your torso and legs need to be involved. That’s why training with medicine balls is so great for your golf swing. Medicine balls are considerably heavier than a golf club, which means you need to recruit more muscle power than your arms can provide if you want to throw one with any force.

How to make medicine ball swings

Pick up a three or four-kilogram medicine ball and simulate your golf swing. Without any conscious effort, your brain will tell your body to immediately get involved in the movement. It changes your neuromuscular recruitment pattern to make the throw happen.

Training with a med ball will especially help you synchronise your downswing, where the legs, hips and core have to move before the arms swing the club into impact.

Two common swing faults can be corrected through medicine-ball exercises, says Steve Evans Jnr, a Golf Digest Certified Fitness Trainer. Evans trains golfers at the Training Ground in the Washington D.C. area. If you sway or slide laterally during your golf swing and tend to hit shots fat or thin, grab a medicine ball with both hands, hold it hip high and face a wall a metre or two in front of you

Throw the ball against the wall in a golf-swing motion. Put some effort into it and feel how your body helps you rotate without losing your balance. If your issue is failing to transfer your weight into your front foot, stand perpendicular to the wall and mimic your golf swing, throwing the ball into the wall.

The key is speed, Evans Jnr, says. Working in slow motion won’t help train the fast-twitch muscle activity needed for swing speed. Two other things to remember when medicine-ball training: 1. Use a ball that is too heavy to throw just with your arms. 2. Even though you only swing in one direction, train in both directions with the medicine ball to improve muscular symmetry. If you’re right-handed, the quality of your left-handed throws doesn’t have to be perfect. Or even close to it. Just do the best you can.

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This article was originally published on golfdigest.com