How a BIOMECHANIST breaks down the golf swing

Learn from the guys at Penn State, Dr Mike Duffey and Eric Handley as they share a quick example of how they work with a student.

Thoughts from biomechanist Dr Mike Duffey

We’re looking at a player that was trying to make it on the European Tour. His swing was reasonably good, but was looking for a little more club head speed.

Below you’ll see the first report we go through, the (kinematic sequence) and what we find is it’s not a true one, two, three, four sequence.

kinematic sequence

What we saw was the arm peaking (purple) noticeably before the pelvis (red) which raises a red flag.

What that tells us is that even though his pelvis peak speed was pretty good, because it was occurring AFTER his arm peak speed he’s loosing the speed he’s generating with his lower body.

That lower body speed isn’t getting transferred up to the arm and ultimately the club.   We’re focused on picking up some speed so this is a great place to start.

On the second graph you’ll see the total moments. The purple and green lines tell us how much energy is going in to create horizontal rotation (green line), which is parallel to the ground, and fontal plane rotation (purple line).

We look for the peak of the green and the peak of the purple to be nearly the same height and for them to occur at about the same time.

What stands out from this graph is that the purple line peaks substantially higher and earlier than the green line.

One thing to notice is right after the top of back swing, it looks like that line was going up and then it dips a little and then it peaks again. When you see sort of a double peak like that in a very short period of time, that’s an energetic loss.

That is a pattern that doesn’t help the golf swing.

Looking at all of this, we can start tying these together a little bit. That green line is really going to help pelvis rotation and the purple line is going to help arm rotation a little bit more. And if you remember back from the previous one, the arm peaked noticeably before the pelvis.


torso graph

Next we’re going to look at torso displacement.

  • Sway is toward or away from the target.
  • Thrust is toward the ball or away from the ball.
  • Then lift is how much it’s moving up and down.

What we noticed here is this players swaying back away from the target and also has very little lift. You can see right after impact the lift (blue line) starts going down indicating they’re dropping down.

The pelvis should be lifting going into impact (that’s a sign of good ground reaction force) and the lift that we see in the torso actually mirrors the lift in the pelvis.

What that told us is the pelvis was coming up, but if it weren’t for that the torso would be diving down. That is indicative of a problem, especially the lift components, a problem with vertical ground reaction force.

So we decided to start there, vertical ground reaction forces.

It was one of probably three or four things that we wanted to work on, but we knew that that would help contribute to some of that early dip that we saw in the purple moment line and help with torso delivery.

By modifying and improving the ground reaction forces, give a better opportunity for the arm velocity to be higher, especially if it was able to peak later.

Taking a look at the old and new kinematic sequence, you can see that the purple line peak is, now above the red instead of noticeably before.

That’s now in a position where the pelvis velocity can still contribute to arm velocity. That is a sign of a better, more efficient swing.

Instead of just trying to create speed between the torso and the arm, the golfer is now taking advantage of the speed of the pelvis, taking better advantage of the speed of the torso, and using that to propel the arm instead of a lot of muscular force to try to accelerate the arm away.

Club head speed went up and angular rotational speed went gone up about 60 degrees per second.

None of this matters if it doesn’t influence ball flight in a positive way.

The ball flight is dictated by the club delivery.

The club delivery is dictated by the movement of the body and the forces that you apply to create that movement of the body. That’s why our lab combines all of those together.


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